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1973 An Ontogenetic Study of Illicium Floridanum (Ellis) With Emphasis on Stamen and Carpel Development. Richard Earl Robertson Louisiana State University and Agricultural & Mechanical College
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Recommended Citation Robertson, Richard Earl, "An Ontogenetic Study of Illicium Floridanum (Ellis) With Emphasis on Stamen and Carpel Development." (1973). LSU Historical Dissertations and Theses. 2494. https://digitalcommons.lsu.edu/gradschool_disstheses/2494
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I I 74-7256
ROBERTSON, Richard E a rl, 1941- AN ONTOGENETIC STUDY OF ILLICIUM FLORIDANUM ELLIS WITH EMPHASIS ON STAMEN AND CARPEL DEVELOPMENT.
The Louisiana State University andAgricultural and Mechanical College, Ph.D., 1973 Botany
University Microfilms, A XEROXC o m p a n y, Ann Arbor, Michigan
© 1973
RICHARD EARL ROBERTSON
ALL RIGHTS RESERVED
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVgp. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AN ONTOGENETIC STUDY OF ILLICIUM FLORIDANUM ELLIS WITH EMPHASIS ON STAMEN AND CARPEL DEVELOPMENT
A D issertation
Submitted to the Graduate School of the Louisiana State University Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Botany
by Richard Earl Robertson B.S., College of the Ozarks, 1965 M.S., Northeast Louisiana University, 1968 August 1973
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENT
The author expresses sincere appreciation to his inajor
professor. Dr- Shirley C. Tucker, for her guidance, patience, and
understanding throughout the course of this study and during the
preparation of this dissertation.
He is also indebted to Dr. Charles A. Schexnayder for his
continued help and encouragement during the entire course of this
stu d y .
Appreciation is also extended to the members of his com
mittee: Dr. Antonios Antonopoulos, Dr. William J. Blackmon, and
Dr. Walter J. Harman.
Thanks are also extended to Mr. Emory Smith, who graciously
provided the specimens for this study from his nursery in Baton
Rouge, Louisiana.
A very special thanks goes to his wife, Pat, for her
continued support and understanding throughout his entire graduate
s tu d ie s .
i i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS
Page
ACKNOWLEDGEMENT...... i i
ABSTRACT ...... v
INTRODUCTION ...... 1
MATERIALS AND METHODS...... 3
RESULTS...... 5
Organography ...... 5
Floral Ontogeny ...... 10
Comparison of Vegetative and Floral Apices ...... 10
B racts and B r a c te o le s ...... 13
T e p a l s ...... 14
Early Ontogeny...... 14
Procambium Development...... 16
V a s c u la riz a tio n ...... 17
Lamina Development ...... 17
Stam ens...... 18
Early Ontogeny...... 18
Procambium Development...... 20
V a s c u la riz a tio n ...... 20
Microsporogenesis ...... 21
Anther Wall Development ...... 22
D eh iscen c e ...... 22
i i i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page
C a r p e ls ...... 22
I n i t i a t i o n ...... 22
Carpel Maturation ...... 23
Camel!& arv* Vasculature...... 25
Procambium Development...... 27
Vascularization ...... 27
Ovule Development...... 28
M egasporogenesis...... 29
Megagametophyte Development ...... 30
Seed and Fruit Development...... 31
The Apical Residuum...... 32
DISCUSSION AND REVIEW OF LITERATURE...... 35
History and Naming of the Genus...... 35
Systematics and Geographical Distribution ...... 35
Relationships ...... 36
The Nature of the Flower...... 37
The Nature of the Perianth...... 41
The Nature of the Stamen...... 43
The Nature of the Carpel ...... 44
The Apical Residuum...... 46
LITERATURE C ITED ...... 49
PLATE LEGENDS...... 53
VITA ...... 117
iv
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT
The ontogeny of the flower and fruit of Illicium floridanum
Ellis was investigated and compared with its vegetative ontogeny.
Each mixed terminal bud produces 5-6 bracts arranged in a clockwise
helix, each bract subtends either a vegetative or floral bud.
Flowers are solitary, occurring either terminally or in an axillary
position. Each flower has 3-6 bracteoles arranged in a clockwise helix
below the floral appendages.
The flower has 24-28 tepals, 30-35 stamens, and usually 13
uniovulate carpels. Tepals and stamens are produced in low-pitched
helices; carpels appear whorled, although there are some indications
that they do not all arise simultaneously or at the same level.
The vegetative apex, which produces leaves and bracts, is
low-convex in outline with a tunica-corpus configuration. The floral
apex is high-convex in outline with a tunica-corpus configuration; it
increases in height and width throughout initiation of the floral
appendages.
Tepals, stamens, and carpels are initiated by one to several
periclinal divisions in the subsurface layers low on the apical
flanks, augmented by cell divisions in the outer layers of the corpus.
Early development wi thin each of the appendages follows a similar
pattern of apical growth by subapical initials. Marginal growth in
all appendages is by definite marginal and submarginal initials,
except in stamens. In tepals, the origin, duration, and cessation
v
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. of marginal and submarginal activity varies, resulting in the ultimate
shape of tepals intergrading from the outer, wide, oblong-shaped
tepals to the inner ones which are narrowly lanceolate with an attenuated
tip. The carpel develops as a conduplicate structure with appressed,
unfused margins; stigmatic papillae form on the greater part of the
adaxial surface of each carpel margin.
Throughout development of floral appendages, procambium develop
ment is acropetal and continuous. Xylem differentiation in tepals,
stamens, and carpels is initially discontinuous. Bracteoles, tepals,
and stamens are each supplied by 1 trace; carpels have 3 traces each:
1 dorsal, 2 ventral bundles.
Sporogenous cells differentiate in a stamen at a height of about
400ju. A vertical column of spore mother cells is surrounded by a
multilayered parietal tissue. Upon completion of meiosis, the 4
microspores within the tetrad separate, each becoming tricolpate,
with a spiny exine. The mature anther wall consists of: epidermis,
endothecium, one to several crushed middle layers, and a tapetum
formed from the inner layer of the parietal tissue. Mature stamens
are laminar with 4-sporangiate introrsely lateral anthers.
Ovule initiation occurs in a median axillary position at the
adaxial base of the carpel, a highly unusual type of placentation.
In its development, the ovule is anatropous, bitegmic, and crassi-
nucellar. The megaspore mother cell usually produces a linear tetrad
of 4 megaspcres; occasionally, a T-shaped tetrad of 4 megaspores is
produced. Subsequently, the 3 micropylar megaspores disintegrate and
the chalazal megaspore develops into the monosporic, 8-nucleate
megagametophyte. v i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fruits develop after flowering in March to maturation in
October. The vasculature of receptacle and follicles is modified
during fruit maturation as the receptacle and follicles enlarge.
After the initiation of the 13 carpels, an apical residuum
persists and continues further development, It loses the tunica-
corpus configuration, and a plate meristem develops over the surface.
A papillate structure forms terminally, with an intercalary meristem
at its base. As the papillate structure is sloughed off, this basal
meristem provides derivatives upward to accommodate the adaxial expansion
of each carpel during fruit development. Among angiosperms whose
ontogeny has been investigated, this activity of the apical residuum
appears to be unique.
v i i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION
Illicium floridanum E llis, the Star Anise, is a member of the
Ranalian family Illiciaceae. This genus shows many primitive flora
characteristics such as numerous appendages, absence of fusion among
parts, radial symmetry, helical arrangement of tepals and stamens,
and a transitional morphological series in members of the perianth.
_I. floridanum possesses one "advanced" floral feature in the apparently
whorled arrangement of the numerous free carpels. The current study
was undertaken to investigate the ontogeny of the flower in I. floridanum
with particular attention to the sequence of initiation of the appendages
and the apparent shift from helical to whorled initiation. Fruit devel
opment and vasculature also were of special interest in this study.
Some aspects of the morphology, anatomy, embryology, and
cytotaxomomy of the genus Illicium have been examined by other authors.
There are few developmental papers on I_. floridanum. Schlotterbeck
and Echler (1901) studied seed and fruit development. Earle (1941)
reported on the development of the embryo and endosperm in the same
species, describing the seed as having a minute embryo with copious
oily endosperm. Bailey and Nast (1948) conducted studies on the anatomy
and morphology of stem and leaves of Illicium , Schizandra, and Kadsura.
Hayashi (1960) presented results of a study on the microsporogenesis
and pollen morphology of Illicium religiosum Sieb. et Zucc. In 1963,
he published results of a study on the megasporogenesis, megagametophyte,
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and embryogeny of X- anisatum L. Keng (1965) studied the floral
morphology, anatomy, and vasculature in six species of Illicium;
1^ floridanum Ellis was not included in his study. Stone and Freeman
(1968) reported in a cytotaxonomic study of I. floridanun Ellis and of
Jt. parviflorum Mich, that for _I. floridanum. the n=13 condition is
probably derived from the basic haploid number of 14 by the process of
aneuploidy. No previous study has been made of the developmental
anatomy of the flower of a member of the genus Illicium . Because of
interest in I. floridanum as a prim itive angiosperm with a somewhat
specialized gynoecium, this floral ontogenetic investigation was
considered of value.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. MATERIALS AND METHODS
Both vegetative and floral buds of Illicium floridanum Ellis
were collected bimonthly from June, 1969, to June, 1970. Collections
were made from plants cultivated in Smith's Nursery, Baton Rouge,
Louisiana. Mr. Emory Smity collected the plants from the west bank
of the Tickfaw River, near Holden, Livingston Parish, Louisiana.
The vegetative and floral apices were killed and fixed in
formalin-acetic acid-alcohol (FAA: 50cc 95% ETOH, 5cc glacial acetic
acid, lOcc 37-40% formaldehyde, 35cc distilled water) and dehyrated
in a tertiary butyl alcohol series. They were imbedded in "Tissuemat",
a high m e ltin g p o in t p a r a f f in , and se c tio n e d a t 7-9ji, on an *'820"
Spencer rotary microtome. The sections were stained with tannic acid,
ferric chloride, and safranin (Foster, 1934) and mounted in "Harleco",
a mounting resin.
Additional flowers and whole carpels of 1. floridanum
were cleared for comparative study of the vasculature. Large carpels
were first bleached in Stockwell's Solution of 5% sodium hydroxide.
Buds and flowers were cleared in either chlorol hydrate or lactic
acid. Special care must be taken when bleaching and clearing using
heat, for the carpels split easily.
Sections and clearings were photographed on Kodak Panatomic X
film using a Leitz Orthomat-Orthoplan photomicroscope with bright-field
illumination.
The width and height of apical meristems were measured on
longitudinal sections with an ocular micrometer. The base of an
3
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. apical meristem, as viewed in longitudinal section, was determined to
be that region above the last formed appendages. The height of a
shoot apical meristem was also determined from transverse sections by
counting the number of 7-9ji sections clearly showing the apical
perimeter above any appendage.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. RESULTS
Organography
Illicium floridanum E llis, the Star Anise (Fig. 1-3), is a
shrub or small tree that ranges from west St. Helena Parish in
Louisiana eastward to Florida and northward to central Alabama (Wood,
1958). The plants in cultivation are evergreen, about 30 years old,
and 4-12 feet high.
The leaves of Illicium studied here are alternate, petiolate,
exstipulate, and glabrous. The leaf shape is simple, entire, elliptic
to lanceolate, and with an acute apex and base (Fig. 3). At maturity,
blade length is 75-150mm and petiole length is 10-25mm; each blade
is decurrent on the petiole. At the end ojf each growing season, the
last 5-7 leaves produced on a stem are often clustered, with very
short internodes. Phyllotaxy is 2/5 in the plants investigated.
The period of greatest vegetative growth of the Star Anise
occurs from March to October of each year.j There are two patterns of
vegetative growth. In a shoot producing aj terminal flower (Fig. 4),
one to several of the uppermost axillary buds are vegetative. These
axillary subterminal buds continue vegetative growth of the shoot the
next year. Several additional flowers, 2-3 in number, may be present | on the branch; each is produced from an axiillary bud below the vegetative
axillary bud and close to the end of the shoot. In the second pattern
(Fig. 5), a shoot has a vegetative terminajl bud and several subterminal
axillary buds in the vegetative state. By the subsequent growth of
many of these buds during the season the shoot undergoes branching.
5
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. An overwintering inflorescence bud in Illicium has 4-6 helically
arranged bracts (Fig. 8). The arrangement is clockwise and phyllotaxy
is 2/5 in the plants investigated. In the axils of some bracts a
floral bud may form. Each axillary floral bud is subtended by 3-6
helically arranged bracteoles (Fig. 9). The arrangment is clockwise
with a 2/5 phyllotaxy in the plants observed in this study.
Within its Louisiana range, the Star Anise flowers during
March and April. The flowers are solitary and either terminal or
axillary. Each flower (Fig. 2, 10) is perfect, hypogynous, radially
symmetrical, and with all parts free. An individual flower has 24-28
tepals, 30-35 stamens, and usually 13 free uniovulate carpels.
Taxonomic descriptions (Redher, 1940; Bailey, 1949; Wood,
1958; Hutchinson, 1959) generally describe the flower of the genus
Illicium as having its parts arranged in several series. It is
difficult to determine if the floral appendages (tepals, stamens,
and carpels) are arranged in a low-pitched helix or whorled. The
difficulty arises from the crowding of the appendages on the receptacle.
The author uses the terms "level" or "series" when referring to the
relative arrangement of the floral appendages; the terms are used for
convenience, without ontogenetic implications.
The 24-28 tepals (Fig. 11) are 20-30mm in length, crimson, and
deciduous. Each has a single midvein. The number of secondary
branches and dichotomies varies according to the length and width of
the tepal. Anastomoses occur rarely, usually in the larger tepals.
The vasculature is open in all tepals.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. If the tepals are arranged in presumptive ontogenetic order,
they fall into morphological groups based on height, width, and
marginal outline (Table 1).
Tepals intergrade in size from the outer long ones to the inner
short ones. In width tepals intergrade from wide outer ones to
narrow inner ones. In outline they range from oblong, rounded-tipped
appendages to narrowly lanceolate ones with attenuate tips. The
vasculature aupply in tepals also shows a gradual modification from
numerous prominent branches in the outer tepals to a single midvein
with few or no branches in the inner tepals.
The androecium consists of 30-35 stamens. Their arrangement
appears helical (Fig. 10). Each stamen is red, laminar, and about
5mm long and 1.7mm wide at flowering. Anthers are basifixed, 4-
sporangiate, and introrsely lateral; they dehisce by longitudinal
slits. The filament is broad and longer than the anther at maturity.
The anther is only slightly wider than the filament and has an attenuated
connective. During anthesis the stamens recurve abaxially at the tips.
The mature pollen is tricolpate, with a spiny exine. The vasculature
of each stamen consists of a single vascular strand that extends to
within a short distance of the tip of the stamen.
Transitions between tepals and stamens occur rarely. (Three
were seen in this study). The anther of a transition appendage varies
in degree of development. Often, only a 2-sporangiate anther is
present, with the incompletely developed sporangial region formed
on the side of the anther closer to the first 4-sporangiate stamen
in the series.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8
Table 1. Tepal size and shape by presumptive developmental order.
Presumptive # H eight Width Shape Tip O rder in mm in mm
O uterm ost 4 24-27 3-5 oblong rounded Group 1
Group 2 8 26-30 4-5 oblong to rounded la n c e o la te
Group 3 4 28-30 4 oblong to ta p e rin g la n c e o la te d i s t a l l y
Group 4 4 26-30 3-4 la n c e o la te ta p e rin g d i s t a l l y
Group 5 4 -8 20-24 3-4 narrow ly a tte n u a te d la n c e o la te tip
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The gynoecium consists usually of 13 free, laterally appressed,
uniovulate carpels. At flowering a carpel is 6-8mm high and 3-5mm
wide at its base. Each carpel has a basally expanded and flattened
ovary with a short, distally attenuated, abaxially recurved style.
The ovary is unilocular. The single ovule is anatropous, bitegmic,
crassinucellar, and is attached near the adaxial base. The stylar
region is conduplicate and connivent throughout carpel and fruit
development; i.e ., it is folded but the appressed edges are not
fused. The stylar region is vascularized and has papillae along the
distal half of its adaxial surface. The vasculature of the receptacle
at flowering in March, consists of closely spaced anastomosing strands
(F ig . 6 ).
The flowers of the Star Anise open during March and April,
and complete fruit maturation by October of the same year. The fruit
is a fcllicetum (Fig. 6, 94) of 13 free, ventrally dehiscing, one-
seeded, spreading follicles, each 14-18mm high and about 15mm wide.
At maturity the fruit is greatly sclerified, dry, star-shaped, and
25-40mm wide. The fruit has an elongate, drooping pedicel 25-100mm
long. The solitary seed of each carpel is oval to sub-reniform in
shape, laterally flattened, 6-9mm long, and with a sub-basal hilum.
Each seed is yellow to brown, glossy, and has a brittle testa. At
the time of dehiscence of the fruit, the seed has copious, oily
endosperm and a minute embryo, near the hilum. No study was conducted
of pollination or germination.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FLORAL ONTOGENY
Comparison of Vegetative and Floral Apices
The vegetative apex in Illicium floridanum is low-convex, as
seen in longitudinal section, with a tunica-corpus configuration
(Fig. 12, 13). Maximum apical width observed was about 250/i; apical
height was 40-60p. The tunica is uniseriate to biseriate and extends
over the homogeneous corpus. By definition, the cells of the tunica
layers divide only anticlinally, while the cells of the corpus divide
in various planes. The cells within the corpus region are isodiametric
and stain more lightly with cytoplasmic stains than cells of the
tunica. In Figures 12 and 13 the 2T (inner tunica layer) contains a
pericli.nal division (at arrow) high on the right flank of the apex;
this is probably the initiatory site of a leaf primordium. With the
leaf primordia initiated high on the apical flanks, the vegetative
apex remains low convex throughout leaf initiation.
In Illicium floridanum, in each flowering shoot the terminal
apex produces several leaf primordia (which each subtend either a
flower bud or a vegetative bud, depending on the type of shoot) and
then undergoes a transition to a floral apex. Most floral apices
arise from axillary buds and do not pass through a vegetative state.
Vegetative and floral apices are easily distinguishable except at the
time oE transition from terminal vegetative apex to flower. The
apical meristem undergoes a gradual enlargement during transition, and
the appendages produced are quite similar in primordial stages. The
earliest recognizable floral apex (Fig. 14) is more highly convex
10
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11
than thn vegetative apex, and is surrounded by many young primordia.
The latter condition clearly contrasts with that of the vegetative
apex (Fig. 12) which has only about 2 leaf primordia adjacent to the
meristem. Cell differentiation is marked in older leaf primordia,
but not in the bracteoles and early tepals clustered around the young
floral apex.
Che floral apex has a tunica-corpus configuration (Fig. 15).
Unlike the vegetative apex, however, the floral apex is high convex
throughout initiation of the floral appendages. It is during the
early activity of the floral apex that apical configuration is least
well defined. Because occasional periclinal cell divisions occur in the
T2 layer of the floral apex, the term tunica is used with reservation.
When first recognizable, the floral apex has 1-2 tunica layers
(T p T 2 ) and a corpus. During floral development, random periclinal
cell divisions (at arrow, Fig. 15) in the surface and subsurface layers
may occur at any point throughout the floral apex rather than being
associated only with initiatory sites. Those far down on the flank
presumably play a role in the initiation of the floral appendages; the
role of those near the summit is enigmatic.
Cell size in the floral apex differs slightly between tunica and
corpus. Cells of the tunica region average 12ji long by 9.6p wide;
their nuclei average 9.5y. long by 8.5ji wide. The cells of the corpus
average 20/i long by 12ji wide; their nuclei average 9.5fi long by 7.2fi
wide. The thickness of the cell walls for cells of both regions is
about 2p. The plane of cell division, the cell files, and the degree
of stainability of the nuclei and cytoplasm, aid in delimiting the two
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12
regions within an apex. The floral apex increases in both width
and height throughout appendage initiation. However, the cells of each
of the two zones remain essentially constant in size. Therefore, it
is the increase in cell number, especially in the corpus, that accounts
for the greatest increase in the size of the apex during appendage
initiation. As the apex increases in size, cell divisions throughout
the subapical region of the axis add derivatives which broaden and
heighten the receptacle to accommodate and support the apical dome
and appendages. Plastochronic fluctuation, if it exists in the flower
of Illicium . could not be documented due to the large number of
appendages being initiated in close succession.
The floral apex of Illicium floridanum increases in size during
the centripetal initiation of all the floral appendages. Before the
initiation of the first 15-17 stamens, the apex has increased in
size to a width of about 375/1 and a height of about 140/1. After the
onset of the initiation of the first 15-17 stamens, the apex increases
in size to approximately 450/1 high by 200/1 wide at the time of
initiation of the second series of 15-17 stamens. After the onset of
initiation of the second stamen series, the apex increases in size to
a width of about 425/1 and a height of about 135/1 just before the
single tier of 13 carpels is initiated.
After the initiation of the 13 carpels, an apical residuum
persists and continues further development. From an initial size of
about 360/1 wide by 105/1 high, it increases to a size of approximately
500p wide by 300/1 high. Subsequent development produces a papillate
process, 500-600/1 high, which eventually sloughs off. This papilla was
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. observed to bear a droplet of secretion in living flowers at anthesis.
While the papilla is forming, an intercalary meristem forms at the
base of the apical residuum. This new meristemitic region provides
cell derivatives that accommodate the adaxial expansion of the
receptacle and carpels. The apical residuum contains no vascular
tissue. The development of the floral appendages, the apical residuum,
and the intercalary meristem is described in later sections.
Bracts and Bracteoles
Throughout its development, an inflorescence bud is surrounded
by 5-6 helically arranged bracts (Fig. 8). Phyllotaxy is 2/5 and in
a clockwise arrangement in the plants investigated. The bracts inter
grade in size, with the outer short bract more massive than the inner
long one. Each o u te r b r a c t i s 7-9mm h igh and 3-5mm wide a t i t s b a s e ,
narrowing and pointed distally. Each inner bract is ll-13mm high and
2.5-4mm wide, with a rounded tip. Each of the 3 outer bracts has a
thicker cuticle than that of the inner bracts. The 3 outer bracts
have epidermal hairs which are heavily cutinized; these are nearly
absent from the inner bracts.
The vasculature in a bract is variable and a function of the
length and width of the bract. A central midvein produces, at interval
3-5 secondary branches. Dichotomies and anastomoses occur occasionally
but not as frequently as in the bracteoles. The major branches of the
vasculature are concentrated in the central region of each bract,
with the marginal regions having few branches. The bracts usually
drop off following anthesis.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14
J!n the axils of the inner bracts,,, single floral buds usually
develop. The outermost bract usually lacks aflower (Fig. 8). Each
floral bud is subtended by 3-6 helically arranged bracteoles (Fig. 8,
9, 14). Phyllotaxy is 2/5 and in a clockwise direction in the plants
investigated. The bracteoles are arranged in a low-pitched helix,
with the inner ones intergrading with the first formed tepals. The
bracteoles undergo precocious cellular differentiation, compared to
the tepals (Fig. 14). Bracteoles average 7mm in length by 3mm in
width, with an oval-oblong outline. The vasculature consists of a
midvein and 2-3 secondary branches diverging at the base. Numerous
branches produce a vasculature that consists of as many as 10-12
closely spaced strands. The first 2-3 bracteoles usually fall off as
the pedicel elongates after flowering, as evidenced by scars on the
pedicel; the remaining bracteoles stay attached to the receptacle
during pedicel elongation. The ontogenetic development of bracts and
bracteoles was not studied.
T ep als
Early Ontogeny
The following description of tepal development is based on
observations of tepals initiated after the floral apex is clearly
recognizable. It was not possible to distinguish the earliest stage
of the floral apex from that of a vegetative apex. Therefore, the
initiatory events leading to the formation of the first few tepals
have not been determined, but are presumably similar to those of the
later tepals.
Tepal initiation begins with one or more periclinal divisions
(at arrow, Fig. 18) in the subsurface layer low on the flank of the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15
floral apex; often, several adjacent divisions in the appear nearly
simultaneously. Cells in the immediate area divide both anticlinally
and periclinally, adding cells to form a protuberance (Fig. 16). The
tepal primordia are initiated in helical succession on a constantly
enlarging floral apex. The exact sequence of initiation among tepals
was not determined. In Figure 19, a transverse section through a
floral bud, the floral apex is surrounded by four tepals, one of which
(at arrow) is in the early stage of marginal and submarginal growth.
The increase in the height of a tepal primordium is initially
the result of general cell division, which is soon augmented by the
activity of apical and subapical initials. These initials originate
when a primordium is about 50p high. The apical in itial divides only
anticlinally and provides derivatives which perpetuate the protoderm.
The subapical initial, which may divide either anticlinally or peri
clinally, adds cells internally. These derivatives differentiate
eventually into the internal tissues of the tepal. When a tepal has
attained a height of 70-80jx (Fig. 17), the derivatives of the subapical
in itial have produced an adaxial and abaxial hypodermal layer and a
middle layer of 2-3 cell layers in thickness. In Figure 17, procambium
has differentiated in continuity with its trace in the receptacle. At
a height of about 350ji, the tepal has a middle layer 4-5 cell layers
wide, and an adaxial and abaxial layer each 2 cell layers wide, as
seen in transverse section (Fig. 20, 21). By a tepal height of 750 —
900fi, a third cell layer has been added to both the adaxial and abaxial
regions, as seen in transverse section (Fig. 22, 23).
Because the tepals curve adaxially early in their development
and because they differ in ultimate height, it was difficult to determine
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. at what height the apical and subapical initials cease to function.
Conservatively, the apical and subapical initials of a tepal may be
said to remain active until the tepal reaches about 800p in height.
The young tepal primordium is at first cylindrical in trans
verse section; it later becomes leaflike as a result of the origin and
activity of marginal and submarginal initials. As the height of the
tepal increases, cell division is more active abaxially than adaxially.
This increased cell division causes the tepal to curve adaxially
(Fig. 17). This condition is observable to a tepal height of about
lOOOp, at which time the tepals grow more erect. The abaxial cells of
the ground meristem soon appear more vacuolate or stain more lightly
than the remainder of the primordium (Fig. 17, 18, 21). Later in
development, dark-staining pigment accumulates in the epidermis, and
many of the cells of the adaxial and abaxial subsurface layers (Fig. 25).
Procambium Development
The development of procambium within a tepal is acropetal and
continuous. The procambium enters a tepal primordium when the primor
dium is 70-80p high (Fig. 17). Throughout the subsequent enlargement
of the tepal, procambium extends to within 50p of its tip. Procambium
enters a tepal primordium in continuity with a procambial strand in the
receptacle. The number of branches from the median procambial strand,
and thus the future number of lateral vascular strands, varies
according to the width of the tepal. The exact sequence of formation
for the minor procambial strands was not determined.
with permission of the copyright owner. Further reproduction prohibited without permission. 17 Vascularization
The differentiation of xylem within a tepal is initially dis
continuous. The xylem differentiates first in the midvein, with
xylem in the lateral branches forming shortly thereafter. The xylem
differentiates in the lowest tepals when they are about lOOOp high.
This is late in floral development, after the carpels are initiated.
Once xylem is present in the outer tepals, the differentiation of
xylem in the other appendages follows rapidly. The sequence of
formation for the secondary branches of the midvein was not studied.
Although the material was not suitable for detailed studies of
phloem development, a few observations can be made. Sieve tube
elements are first visible at the same time and level as the first
xylem elements, in the base of each tepal. Phloem appears to differ
entiate throughout the tepal as it enlarges at the same time as xylem
is differentiated. The sieve tube elements are quite narrow and
elongate, and lack the "nacre" or thickened wall found in some other
prim itive Ranalian taxa such as Magnolia and Liriodendron.
Lamina Development
The development of the lamina of a tepal is the result of the
activity of marginal and submarginal initials. The marginal initials
divide only anticlinally and produce derivatives that mature into the
epidermis of the tepal. The submarginal initial divides anticlinally
and periclinally, with its derivatives increasing the width of the
la m in a .
The marginal and submarginal initials originate when the tepal
promordium is about 250p high (Fig. 19). As derivatives of the marginal
and submarginal initials are produced, the shape of the tepal, as seen
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in transverse section, changes from circular to ellipsoidal (Fig. 20,
21). Further development produces a crescent-shaped lamina (Fig. 22).
In later tepal development (Fig. 22-24), the tepal widens but
remains approximately the same thickness. Marginal initials continue
to function after the submarginal in itial becomes inactive, producing
a thin margin 2 cells thick (at M, Fig. 22-24). The thin margins are
more pronounced in the outermost tepals (Fig. 24).
Although when mature the tepals differ in length, width, and
shape, no early developmental differences are observed among the
tepal primordia. Because the tepals intergrade from outer, wide tepals
to inner, narrow ones, the duration of activity for both marginal
and submarginal initials can be assumed to be the main variable
factor responsible. Maturing tepals (Fig. 25) are comprised mostly
of highly vacuolate parenchyma, with scattered dark-staining pigmented
cells. The vasculature in the tepal in Figure 25 is not well formed
at this stage of development.
Stamens
Early Ontogeny
At the beginning of the stamen initiation, the floral apex is
about 375ji wide and 140p high (Fig. 26). Although the 30-35 stamens
appear helically arranged (Fig. 10), they are referred to two "series"
for convenience in this study. Usually 2 (rarely 3) stamen primordia
are present in a flank in median longisection; the outermost is part
of the first series, and the innermost is part of the second series.
The first 15-17 stamen primordia are initiated in helical succession
on the flanks of the floral apex as evidenced by transsectional views
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(Fig. 10, 29). The last-formed tepal primordia are 80-100p high
when the. first stamens are initiated. Just preceding initiation
of the second series, the apex is 450p wide and 200p high (Fig. 27).
As the second 15-17 stamen primordia are initiated in helical
succession, they lie approximately alternate in position with previously
initiated stamens (Fig. 30). After initiating the last stamen
primordia, the floral apex is about 370p wide and 135p high. At
this time, the last formed tepals are about 175p high.
The initiation and ontogeny of the 30-35 stamen primordia is
similar for all; therefore, the subsequent discussion applies to the
development of any of the stamen primordia. A stamen primordium is
initiated by a periclinal cell division in the subsurface layer low
on the flank of the floral apex (at arrow*in Fig. 27). Cells in the
initiatory area, which often stain more intensely than surrounding
cells, divide in various planes and produce a protuberance (Fig. 31,
3 2 ).
A stamen primordium increases in height by localized cell
divisions at its tip until it is 40-50ji high (Fig. 28, 31, 32). The
apical and subapical initials originate when a stamen primordium is
40-50p high (at arrow in Fig. 33). They continue apical growth of the
stamen primordium until it is 400-450p high, when the apical initials
cease to function. The apical initial divides only anticlinally and
gives rise to the protoderm of the stamen. The subapical initial
divides both anticlinally and periclinally and gives rise to the
internal tissue of the stamen.
A stamen primordium is rather blunt apically, while tepals are
more pointed. As a stamen primordium increases in height, it curves
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adaxially, similar to a tepal primordium (Fig. 34). On the stamen at
far right in Figure 34, the ground meristem cells on the abaxial side
of the stamen have begun to differentiate and enlarge. This stamen is
cut medianly, so the procambium is shown within the base of the stamen.
Procambium Development
The development of procambium in a stamen is acropetal and
continuous in all stamens. A single procambial strand is at the base
of a stamen primordium when the primordium is 25-30ji high (Fig. 35,
36); procambium differentiates in a primordium when it is about 50ji
high. The procambium enters from strands in the receptacle which have
differentiated above the level of the tepals. A common sympodium
may supply a tepal and a stamen of the second series (at arrow in Fig.
37). First and second series stamen primordia may also have a common
sympodium. The procambial strand extends to within 50p. of the tip of
the developing stamen.
Vascularization
The differentiation of xylem within stamens of both levels
i:: initially discontinuous. The xylem differentiates in stamens of
the first series when they are about 400ji high (Fig. 42). The differ
entiation of xylem in the stamens of the second series also occurs
when they are about 400ji h ig h .
The phloem differentiates in the stamen at about the same time
as the xylem at any one level. The question of initial continuity
was not resolved.
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Microsporogenasis
Mature stamens are red, with a broadened filament and a 4-
sporangiate, introrsely lateral anther (Fig. 38, 41). The broadening
of the stamen during development is the result of general cell division
and differential enlargement; no specialized marginal and submarginal
initials were observed in the stamen. (Compare Fig. 39, 40).
When a stamen is about 400ji high, sporogenous cells form in
the regions of the anther. There are 2 sporogenous regions formed in
Figure 43. Figure 42 shows these areas in longitudinal section. In
Figure 44, a transverse section through the developing anther of a
stamen, a sporogenous cell (at arrow) is surrounded by a single parietal
layer. The repeated divisions of the sporogenous cells through the
anther region produce a vertical column of spore mother cells 3-5 cells
across. These regions of sporogenous cells are seen in transverse
section in Figure 45, 46. With the repeated periclinal divisions of
the cells of the parietal layer, each group of sporogenous cells
becomes surrounded by a multi-layered parietal tissue (Fig. 45, 46).
The inner cell layers of the parietal tissue eventually differentiate
as the wall of the pollen chamber. Prior to the first meiotic division,
the spore mother cells separate from their previously clustered
arrangement (Fig. 47, 48).
The division of the spore mother cells in microsporogenesis is
simultaneous and follows the regular meiotic sequence. With the first
meiotic division, a dyad is formed (Fig. 49). The second meiotic
division produces a tetrad (Fig. 50). Prior to separation, the
cytoplasm shrinks from the walls of the tetrad cells (Fig. 51, 52).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. With the separation of the microspores, each becomes tricolpate, with
three external grooves and a spiny exine. The pollen in Figures 39-41
appear collapsed, but this is an artifact. A division of the nucleus
and cytokinesis produces a 2-celled pollen grain at the time of
d is p e r s a l.
Anther Wall Development
As pollen development proceeds, the layers of the anther wall
are maturing. At maturity, the anther wall consists of: epidermis,
endotheclum, one to several middle layers, and a tapetum (Fig. 52).
The tapetum forms from the inner layer of the parietal tissue (Fig. 45)
rarely, it is irregularly 2-layered. During pollen maturation, the
middle layers of the wall of the pollen chamber are gradually crushed
and the cells of the endothecial layer increase in size (Fig. 46-52).
D ehiscence
Pollen grains mature within the pollen chamber before anthesis
ir March. Dehiscence of the anther occurs either slightly before
flowers open or very soon thereafter. Observations of flowers during
anthesis reveal that the stigmatic areas of all carpels are reflexed
abaxially. The stamens, with their dehiscing anthers, are often erect
and in close proximity to the attenuated, reflexed stigmatic surfaces
of the carpels. Pollinators were not observed.
Carpels
I n i t i a t i o n
At initiation of the carpels, the floral apex is approximately
425p wide and 135 ji high. At the initiation of the carpel primordia,
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each stamen of the second tier is about 140p high, and each stamen of
the first tier is about 180p high. The most recently formed tepals
are 500-600p high.
The 13 carpel primordia are initiated very closely in time and
level in each flower. In Figure 53, a longitudinal section through
the floral apex, two adjacent periclinal cell divisions (at arrow)
are present in the second layer low on the left flank. Considerable
cell division occurs at the intiatory site to a depth of 5-6 cell
layers (Fig. 54, 55) before a protuberance forms. The carpel initials
and their immediate derivatives, soon produce a protuberance (Fig. 55,
57). One indication against whorled initiation is that carpels differ
in height at a very early stage, although these differences disappear
later on. Evidence suggests that carpel initiation is rapid; in
Figure 56, all the carpel primordia, as viewed in transverse section,
are in one plane of section.
Carpel Maturation
The increase in the height of a carpel to 50-60p is the result
of a meristematic region at the distal end of the developing carpel.
At a height of about 60p (at arrow in Fig. 57), a carpel develops a
subapical initial. The subapical initial divides both anticlinally
and periclinally, with the derivatives adding to the internal regions
of the carpel throughout its early growth. When the carpel attains a
h e ig h t o f 8 0 0 - 1 0 0 0 ^1 , the activity of the apical and subapical initials
are no longer observed as other meristems become active.
The growth of the young carpel is initially outward and then
upward (Fig. 57, 58). To a height of about 300-350p, differential
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growth throughout the carpel, augmented by marginal and submarginal
activity, produces an elongate, basally expanded structure (Fig. 59).
Prior to the initiation of marginal and submarginal activity,
a carpel is cylindrical to oval in transverse section through
most of its length (Fig. 60). At this stage in development, the
carpel is widening basally by generalized cell division. Throughout
floral development, the receptacle increases in size and accommodates
the initiation and expansion of all the floral appendages.
During the initial increase in the height of a carpel, an
attenuated tip is produced. Often the cells along the distal,
adaxial surface of the carpel divide faster than cells on the abaxial
side. This preferential cell division causes the tip to curve abaxially.
During the remainder of carpel and fruit development, a carpel often
retains this small, recurved tip.
When a carpel is about 150-200p high, (at arrows in Fig. 60),
marginal and submarginal initials originate. Through differential
growth, the adaxial margins of each carpel become folded through the
greater part of its length. By appression of the adaxial surfaces,
the carpel becomes conduplicate (Fig. 61). Throughout carpel develop
ment, the conduplicate margins in the distal region are appressed
but not fused (Fig. 61-63).
During the appression of the carpel margins, further expansion
continues as a result of localized cell divisions throughout the
carpel. Generalized cell divisions in the adaxial and abaxial regions
of the carpel expand it radially, as seen in transverse section
(Fig. 61-63). Prior to the initiation of the ovule, adaxial plate
meristems form in the appressed carpel margins (Fig. 64). The
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periclinal cell divisions within this plate meristem build up the
basal part oE the adaxial surface of each carpel margin. The
expansion continues through maturation of the carpel in fruit develop
ment. The further development of the carpel is described in a later
section on fruit maturation.
Carpellary Vasculature
The vasculature ground-plan of a carpel is only partially
complete at anthesis; the vasculature becomes further modified during
fruit development. Prior to anthesis, there is a single dorsal
strand that extends to within a short distance of the tip of the
carpel. Two secondary branches diverge from the dorsal strand close
to the base of the carpel. Each branch follows the abaxial side of
the carpel and terminates midway up the style. The degree of
curvature is more pronounced as the carpel matures in fruit development.
The ovule, and the subsequent maturing seed, are supplied
directly by at least one ovular branch that terminates in the funiculus
at the base of the hypostase. The main ovular strand diverges from
the first ventral strand.
Each of the 2 ventral strands branch close to the carpel
base. The ventral strands and their branches extend along the
adaxial surface and terminate in the stigmatic region of the carpel.
Minor branches from the ventral strands curve and terminate in the
region of the presumptive seed prior to flowering. The vasculature,
at the time of flowering, is shown in the cleared carpel in Figure 65
and 66.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26
At the time of flowering, the vasculature of a carpel is
incompletely formed. Subsequent to anthesis in March, and until
October, when fruit development is completed, the vasculature is
augmented by new branches. Comparison can be made between the
vasculature in the carpels in Figures 65 and 66, which are at
flowering in March, with the June vasculature in the young follicles
in Figures 67 and 68. As the greatest expansion of the carpels
occurs after flowering, the vasculature changes as the carpels
increase in size.
As the carpel expands during fruit development, there is an
occasional bifurcation of the dorsal strand in the region of the
style. Additional branches may also diverge from the major secondary
branches of the dorsal strand. These, as with much of the vasculature
forming from the dorsal strand, recurve strongly and terminate close
to the developing seed. Rarely, there are minor anastomoses between
the smaller, secondary branches and that of the dorsal strand. As
with the branches of the dorsal strand, ovular branches may rarely
produce one or two minor branches. During the maturation of the
carpel in fruit development, each ventral strand produces additional
minor branches close to its base. These branches increase in number
as the base of the adaxial surface of each carpel is expanding.
Several minor branches of the ventral strands curve and terminate
close to the maturing seed. The vasculature in a carpel, therefore,
develops to its greatest extent during fruit and seed development.
Seed presence is not, however, a prerequisite, since much of the
vasculature still forms in carpels containing abortive seeds.
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Procanibium Development
The development of procambium within a carpel is acropetal
and continuous. The procambium is situated immediately below a
carpel primordium when it is about 50ji high (Fig. 69). It develops
within the primordium when it is 70-80p high (Fig. 70). It con
tinues to develop within about 45}i of the tip of a carpel as the
carpel enlarges (Fig. 71). Procambium forms first in the median
dorsal strand and its branches. The procambium development then
proceeds acropetally in the ovular and ventral strands. The exact
sequence of procambial development for the numerous branches of the
dorsal strand and the two ventral strands was not studied.
Vascularization
The formation of xylem within a carpel is initially discon
tinuous. The xylem differentiates within the carpels, after members
of the second stamen level have been vascularized. A carpel is 300-
350ji high when xylem begins to develop within it.
Xylem differentiates first in the dorsal strand (Fig. 71).
D ifferentiation of xylem in the dorsal strand extends to within a
short distance of the tip of the carpel. The differentiation of
xylem in the secondary branches of the dorsal strand occurs shortly
thereafter. Xylem then differentiates acropetally to the ventral
strands. Xylem supplying the region of the ovule is seen in Figure
72. Subsequent to flowering in March, during fruit development,
xylem differentiation becomes much more extensive throughout the
carpel (Fig. 67, 68).
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Initial phloem differentiation was not determined for the
carpel. Sieve tube elements are differentiated usually at the
same level as tracheary elements in the carpel at any one time.
Ovule Development
When the carpel is approximately 300-350ji high, a solitary
ovule is initiated. The ovule originates medianly at the adaxial
base of the carpel. The initiatory site is axillary in position.
It is between, but not attached to, the appressed margins of the
carpel; i.e ., the appressed carpel margins surround and overtop
the initiated ovule. The initial increase in size of the primordium
is the result of general cell division throughout (Fig. 73, 74).
At a height of about 80p (Fig. 75) a subapical initial originates
in the ovule and augments further growth.
The orientation of the ovule is erect during the initiation
and early development of the megaspore and the 2 integuments.
During megasporogenesis, the ovule bends downward and is completely
inverted, in anatropous position, during the development of the
megagametophyte (Fig. 87). Procambium forms within the funiculus
when an ovule is about 100-120^1 high (Fig. 64). It extends to the
base of the hypostase during the development of the ovule (Fig. 87).
Xylem eventually differentiates to the base of the hypostase. As
ovular development continues, a plate meristem, formed along the
adaxial surface of the appressed carpel margins, adds cell deriva
tions that build up the margins (Fig. 64). Throughout development
the carpel margins surround the ovule and form, by their appression,
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a unilocular region within which the ovule develops. Throughout
carpel development, fusion of the appressed margins does not occur.
The ovule is bitegmic. The inner integument forms first, and
is protodermal in origin. Prior to initiation of the inner integument,
the cells of the protodermal layer elongate anticlinally, with respect
to the main axis of the ovule (Fig. 81). The outer integument forms
on the adaxial side of the ovule by periclinal divisions in the second
layer. In Figure 81, a single periclinal cell division is within the
plane of section at the left side of the ovule; this is part of the
ring of cells initiating the outer integument. The outer integument
encircles the distal part of the ovule like a cap. As development
proceeds, the inner and outer integument is extended in growth and the
megaspore becomes functional (Fig. 82). In Figure 83, the plane of
section is through the adaxial rim of the outer integument. As the
integuments develop further, their margins appress distally around a
micropylar canal. At anthesis the outer integument has 5 cell layers;
the inner integument has 3 cell layers (Fig. 87). The development of
the integuments in the maturation of the seed coat is described in a
later section.
Mugasporogenesis
A carpel is 1000-1200)1 high and the ovule about 200p high when
megasporogenesis begins. A periclinal cell division in the hypodermal
layer of the ovule produces an archesporial cell (Fig. 80). This cell
expands and vacuolate (Fig. 81, 82). A periclinal division of the
archesporial cell forms a parietal cell (at arrow in Fig. 84) and a
sporogenous cell. The sporogenous cell functions as a megaspore
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mother cell. Cells distal to the megaspore divide periclinally and
form a nuceiLus that consists of several layers (Fig. 85, 86).
Initiation and development of the megaspore is crassinucellar, i.e.,
the megaspore is initiated from a subsurface cell and is ultimately
covered distally by a multilayered nucellus.
The first meiotic division of the megaspore mother cell forms
a 2-nucleate stage (at arrow>in Fig. 85). A second division forms
a linear tetrad of 4 megaspores (Fig. 86). Three of the 4 megaspores
are in the plane of section in Fig. 86. Occasionally a T-shaped
tetrad of 4 megaspores occurs. Subsequently, the 3 micropylar
megaspores disintegrate and the chalazel megaspore begins to divide
to form the megagametophyte.
Megagametophyte Development
Subsequent to the development of the functional chalazal
megaspore, the 8-nucleate megagametophyte is formed by 3 mitotic
divisions of the megaspore nucleus. With the third division completed,
the 8 nuclei become rearranged within the embryo sac. The 3 ephemeral
antipodal nuclei assume a position opposite that of the micropyle.
Occupying a central position are the 2 polar nuclei. These fuse
eventually to form a central nucleus (Fig. 87). The remaining 3
nuclei assume positions near the micropylar end as the egg apparatus
(Fig. 88). The largest of these nuclei is the egg, positioned between
2 synergids. During the development of the megagametophyte stage,
the dividing nuclei are seldom all in the same plane of section.
Throughout development of the megagametophyte stage, the dividing
nuclei have no apparent cell walls surrounding them. Thus, development
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of the embryo sac in lllicium conforms to the monosporic, 8-nucleate
Polygonum type.
Seed and Fruit Development
The development of the fruit of lllicium floridanum E llis was
investigated over 70 years ago by Schlotterbeck and Echler (1901).
Earle (1941) studied the development of the embryo and endosperm in
the same species. Because of these earlier studies, the development
of the embryo and endosperm was not studied in detail. The discussion
to follow describes only the salient developmental features of these
structures.
Seed development occupies the period between flowering in
March through fruit maturation in October. Figure 89 shows the zygote
prior to the first cleavage. Figure 90 shows early endosperm.
Earle (1941) says endosperm development is cellular, and the embryo
development is of the Asterad type.
The formation of the seed coat occurs by further modification of
the inner and outer integuments (Fig. 91-93). The outer integument
has 5 layers. The non-pigmented cells of the outermost layer elongate
anticlinally and develop thickened walls (Fig. 79); the remaining 4
layers become filled with pigment (Fig. 91-93). The inner integument
has 3 layers. The cells of the outermost layer enlarge slightly and
become pigmented; the other 2 layers become crushed (Fig. 91-93).
With the 13 carpels arranged in a whorl, expansion of carpels
during fruit development results in the close appression of lateral
walls. The greater expansion of each carpel occurs vertically and
radially, with tangential expansion limited by crowding of neighboring
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carpels (Fig. 94). As expansion proceeds there are differences among
carpels as to shape, height, and size because of crowding.
Each carpel is attached by its base to the conical receptacle.
Fusion between carpels does not occur. As viewed from above (Fig. 94
L, m) the mature follicetum is stellate, with each follicle oriented
with its narrow base attached to the receptacle. Each follicle is
lenticular in shape.
With maturation complete, the individual sclerified follicles
begin to dry and dehisce ventrally. Throughout fruit development
the adaxially folded carpel margins (now horizontally oriented) do not
fuse. As the less sclerified basal region of each carpel dries, tension
is exerted against the marginal regions of the carpel. As drying
continues, the margins separate adaxially and expose the seed. The
seeds are expelled apparently by differential drying. The sclerified
follicetum remains attached to the branch for some time.
The vasculature of the receptacle is augmented in fruit develop
ment. Subsequent to anthesis, the receptacle expands and accommodates
the maturation of the carpels into fruit. Initially, the receptacular
strands of xylem are close together. As expansion of the receptacle
occurs, the bundles become separated more widely. In Figure 95, a
cleared preparation of a carpel in June, the intervascular space is
greater than that at flowering in March (Fig. 6).
The Apical Residuum
After the initiation of the 13 carpel primordia on the apical
flanks, the apical residuum persists as a raeristem and continues further
development (Fig. 96-98). From an initial size after carpel initiation
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of about 360ji wide by 105ji high (Fig. 96), the apical residuum increases
to a size of 500ji wide by 300ji high by the time the carpels are 350p.
high (Fig. 99). Periclinal divisions buildup the flanks of the residuum
(Fig. 96). The residuum becomes truncate as a result; cell files
radiate toward the surface and the tunice-corpus configuration is lost
(Fig. 99). It is replaced by a plate-meristem over the residuum.
The cells of the former tunica undergo divisions in both periclinal and
anticlinal planes. Subsequently, cells in the radiating files become
elongate and their contents lose their meristematic appearance and
become dark-staining and/or vacuolate (Fig. 100). The exact nature
of these tannin-like substances was not determined. The elongation of
the subsurface cells in the central summit region (Fig. 101, 102)
eventually produces a high-domed structure with papillate summital
cells (Fig. 103). The surface cells eventually collapse and slough
off (Fig. 104, 105); in some flowers the entire papilla is lost
(Fig. 106).
During the development of the apical residuum, an intercalary
meristem develops. The meristematic region becomes gradually restricted
to the base of the apical dome, while surface cells become differentiated
(Fig. 102, 103). The basal meristem acts as an intercalary meristem.
The meristem consists of cells which divide predominantly periclinally.
The meristem supplies additional cellular components to the summital
process (Fig. 90). It continues to supply cell derivatives upward
after the papilla is sloughed off (Fig. 106). With the subsequent
expansion of the carpels during fruit development, the intercalary
meristem adds cell derivatives that accommodate the adaxial expansion
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of the receptacle and carpels (Fig. 106). The cell derivatives
from the intercalary meristem eventually become sclerified during
fruit development, as does the greater part of the carpel.
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DISCUSSION AND REVIEW OF LITERATURE
History and Naming of the Genus
The genus lllicium L. was first mentioned in the western
literature by Clusius in 1601 (Smith, 1947). He applied the name
Anisum Philippinarium insularum to what is today recognized as lllicium
verum Hook f., the fruit of which has been used for centuries in the
Orient to enhance the flavor of food. Linnaeus (1759) proposed
the valid generic name lllicium in his Systema Naturae, Tenth Edition.
The type species is _I. anisatum L.
Systematics and Geographical Distribution
Today, the genus lllicium is placed in the family Illiciaceae,
due largely to the studies of Bailey and Nast (1945, 1948) and Smith
(1947). Within the genus, Smith (1947) recognizes two sub-divisions
based on the characteristics of the perianth lobes. In the section
Badiana Spach, the inner perianth lobes are thin, narrow, and somewhat
lax at anthesis. In the section Cyiribostemon (Spach) A. C. Smith, the
inner perianth lobes are ovate to suborbicular and rarely lax at
anthesis. In the western hemisphere the ranges of both sections are
separate (Smith, 1947). The section Cymbostemon occurs in central
Florida, eastern Cuba, and Haiti. The section Badiana occurs in the
southeastern United States (Alabama, Florida to Louisiana), and
eastern Mexico. Of the 13 species of lllicium in the section Badiana,
2 are American: I_. floridanum E llis, the Star Anise, and _I. mexicanum
A. C. Smith. Of the 29 species of lllicium that comprise the section
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Cymbostcmon, 3 arc American: parviflorum Michx. cx Vent., the
small-flowered Anise-seed tree, 1^. ekmanii A. C. Smith, and I.
eubense A. C. Smith, the Cuban plant referred to as Anise.
Relationships
Both Smith (1947) and Bailey and Nast (1948) consider the
Schizandraceae, with the 2 genera Schizandra and Kadsura, to be most
closely related to the Illiciaceae. In comparing the taxonomic charac
ters of the 2 fam ilies, Smith (1947) alludes to their probably common
ancestry and relates that in their development each retains certain
primitive characters while concomitantly modifying others.
Several points of comparison can be made at the family level
between the Illiciaceae and the Schizandraceae. Whereas the members
of Illiciaceae are shrubs or trees, bearing hermaphroditic flowers,
the members of Schizandraceae are woody vines with unisexual flowers.
In the Illiciaceae, the receptacle of the flower is little modified
after anthesis; in the Schizandraceae, however, the receptacle of the
female flower is greatly elongated in fruit.
The carpel arrangement in the Illiciaceae consists of a single
whorl of 7-15; in flowers of the Schizandraceae, the carpels are
numerous (12-300). The style, in members of the Illiciaceae, is
conduplicate, ventrally stigmatic and vascularized; in the Schizandraceae,
there is essentially an unvascularized, conduplicate pseudostyle with
closely approximated ventral stigmatic crests.
The fruit of the Illiciaceae is typically a follicetum consisting
of free-spreading follicles dehiscing ventrally; the fruit of the
Schizandraceae, however, is an aggregate composed of an elongate receptacle
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usually single, ellipsoidal or obovoid in shape, laterally flattened,
and with a subasal hilum. The seeds of the Schizandraceae are usually
paired, immersed in the fleshy pulp of the pericarp, ellipsoid-
subreniform in shape and with either a ventral or superior hilum.
The Nature of the Flower
Both phylogenetic as well as ontogenetic approaches have been
used in attempts to evaluate the many interactions preceding as well
as following anthesis. Thomas (1936) considered the flower not to be
homologous to a vegetative bud. He suggested that since ancient
plants were known to have borne sporangia at the "tips" of naked
stems, the phylogenetic development of the reproductive structures
was independent of that of the leaf. The reproductive structures
evolved, in his view, from fertile branch systems equivalent with the
branch systems that gave rise to leaves. Melville (1962, 1963) also
supported the non-homologous concept, suggesting that selected flowers
resemble compound strobili or fused branch systems.
Eames (1929, 1931, 1961) was the outstanding modern proponent to
equate the flower to a shoot; he considered that the flower consists
of a short, determinate axis bearing modified appendages. The earlier
viewpoints since the time of Goethe are summarized in reviews by
Bancroft (1935), Wilson and Just (1949), and Maeliono (1970). According
to this theory, both floral appendages and leaves are considered to
be homologous appendicular structures that have developed along parallel
lines of evolution.
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The primitive flower is alleged to have been bisexual, with an
undifferentiated perianth, numerous stamens and carpels, and with
all parts free and helically arranged (Eames, 1961; Esau, 1965;
Bierhorst, 1971). Flowers with spiral arrangement of all parts are
rare, occurring for example in some Magnoliaceae and Winteriaceae.
The androecium alone or together with the gynoecium more commonly
exhibits spiral arrangement, especially in families such as the
Ranunculaceae, Dilleniaceae, Rosaceae, Winteraceae, Nymphaeaceae,
and Magnoliaceae. It is suggested by some authors (Church, 1920; Esau,
1943; Leppik, 1961) that the floral organs of a plant are not neces
sarily arranged in terms of phyllotaxic patterns similar to the
phyllotaxy of vegetative shoots. lllicium floridanum fits the
concept of a primitive flower in having numerous free tepals, stamens
and carpels. Each series of appendages is arranged along a very
low-pitcbed helix. With the crowding of the appendages on the short
receptacle, phyllotaxy is difficult to determine. The carpels appear
whorled at all stages, but some evidence suggests a tendency toward
spirality. The 13 carpels appear to initiate nearly simultaneously,
based on the lack of any stages showing only a portion of the total
number of primordia. The youngest carpels observed, however, showed
variation in carpel height (from 20u to 30u), and they differed
slightly in base level in the receptacle and in level of trace diver
gence. These initial variations become indistinguishable at later
stages of carpel development, leading most observers to assume the
carpels are whorled. In _I. floridanum, the arrangement of the floral
parts is probably in transition from helical arrangement of parts to
that of whorled arrangement, at least in the gynoecium.
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Additional evidence on the nature of the vegetative shoot and
its appendages, leaves and bracts, suggests that the vegetative apical
meristem is also one undergoing gradual transition. Leaves are
initiated in a 2/5 phyllotaxy in a clockwise direction. At the end
of the growing season, the last 5-7 leaves are clustered at the end
of a branch with short intemodal regions. The arrangement of bracts
is also in a clockwise direction with a 2/5 phyllotaxy. However, there
is far less internodal elongation between bracts than between leaves.
In their general appearance and internal vasculature, leaves and
bracts share similar characteristics, just as similar characteristics
are shared by bracteoles, tepals and stamens. In 1^. floridanum.
therefore, there is a gradual but noticeable modification of both the
vegetative and the floral apex during initiation of their respective
appendages, accompanied by a decrease in the pitch of the helices
associated with initiation of parts.
Gregoire (1938) asserted that a floral apex is an entirely new
apex arising de novo upon a shoot apex. Plantefol (1948) believed
that the corpus expands above the receptacle to form emergences which
become floral organs. Buvat (1952) considered that at the time of
floral onset, the tunica enlarges greatly and spreads out over the
surface of a new mass of cells formed by the corpus. In 1^. floridanum,
a tunica-corpus configuration occurs in both the floral and vegetative
apex. Initiatory sites may be large, with the primary periclinal
division(s) in the ^ augmented by deeper divisions in the other
corpus layers.
The floral apex of many plants exhibits a mantle-core configura
tion (Philipson, 1947; Boke, 1948; Tepfer, 1953). In these plants, the
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apices with central, peripheral, and rib meristematic zones, become
reorganized into a mantle-core configuration at the time of floral
inducation. It is suggested that the floral apex is not structurally
different from that of the shoot apex and that it has both structural
and functional continuity with the shoot apex. It is further suggested
that reorganization of the existing meristematic cells occurs by a
gradual transformation. The floral apex in I. floridanum enlarges
gradually but remains structurally unchanged internally during
initiation of the floral appendages. The intergrading of the form of
bracteoles, tepals and stamens suggests a gradual physiological
modification in the structure of the floral apex.
The shape of the receptacle of a flower ranges from axial
(Magnoliaceae) to high dome-shaped (certain Ranunculaceae, Nymphaeaceae)
to short-domed (probably the majority of angiosperms), to cup-shaped
(Calycanthus), to almost non-existent, as in the microsporangiate
flowers of many species. In lllicium floridanum, the axis of the
receptacle of the flower is short. During the development of the
floral appendages, and during fruit production, the receptacle
expands only slightly and accommodates and supports the developing
structures. There is little elongation of the receptacle in fruit
production, as occurs in the Schizandraceae.
The number of carpel traces is somewhat difficult to determine.
The interface between receptacle and adaxial carpel base is very
broad. Because of this difficulty, it is difficult to decide whether
1 or 3 traces diverge from the receptacle into the carpel; 3 main
strands are present per carpel: the dorsal, which diverges on the
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abaxial side of the carpel, and 2 ventral strands into each of the
carpel margins.
Abscission of floral parts has not been investigated as much
as that of leaves, but the process of separation appears similar.
Parts or entire structures may absciss at various stages in the
reproductive process. After flowering, shedding of parts of the
flowers or entire flowers may occur. Petals are shed in many flowers,
falling without previous wilting (Aquilegia) or abscissing in a wilted
or dried state (Lilium). If petals are not shed at the end of flower
ing, they may remain attached to the fruit for some time, as in
Agapanthus. Sepals, staminal filaments, and styles may absciss after
flowering in a manner similar to that of the petals. Flowers may
fall singly or as entire inflorescences. If fertilization fails to
occur, carpellate and bisexual flowers may also drop. Abscission
of floral parts is general in I. floridanum. Abscission usually occurs
early in the bracts and bracteoles. Tepals and stamens, however,
absciss shortly after anthesis. The carpels usually do not absciss
after flowering even when the seed within some of them aborts. The
pedicel of the fruit, after seed dehiscence, may remain attached to
the stem for some time.
The Nature of the Perianth
In certain plants, the perianth is undifferentiated, and the
appendages are referred to as tepals. In Calycanthus (Dengler, 1972)
which superficially resembles the flower of lllicium , the tepals
(approximately 30) are linear and fleshy and arranged helically on the
rim of the concave receptacle. They show a similar transitional series
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varying in size and form, with staminoid features on the innermost
t e p a l s .
Tepals are generally more leaflike than other floral appendages,
both in vasculature and mature form. They may intergrade from leaflike
to stamen-like structures. Each tepal is usually supplied by 3
vascular traces that diverge from the receptacle; the solitary trace
per tepal in floridanum is unusual in this respect.
The initiation and early development of sepals and petals
are similar to those of leaves (Boke, 1948; Tepfer, 1953; Tucker,
1959). In their growth, the perianth parts of a flower exhibit apical
activity of a short duration followed by some intercalary growth.
Marginal activity, augmented by intercalary growth, increases the
width of the tepals. Final form of the perianth members is the result
of differential growth and enlargement.
Where petals occur in certain monocotyledons and in some
dicotyledons (e. g. woody Ranales), they are alleged to have arisen
by differentiation of sepals or as a modification within an undif
ferentiated perianth. In other dicots, such as the Ranunculaceae and
Rosaceae, the petals presumably arose by modification of stamens.
Frequently, there are transitional forms between petals and stamens,
and commonly both petals and stamens are each supplied by a single
trace. This suggests to some that in certain taxa the petals have
evolved from stamens. In a more unusual case, intermediates between
stamens and carpels are formed, as in Salix; in each carpelloid stamen
there is a short style and stigma. The most complete transitional
series between the appendages of the corolla and androecium occurs in
the Nyirphaeaceae, in which all the floral appendages as a basic
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condition are each supplied by 3 traces (Moseley, 1958). In 1^.
floridanum, there exists a transitional series between the bracteoles,
tepals and stamens, each with 1 trace.
The Nature of the Stamen
According to the classical floral theory, leaflike floral
appendages are alleged to be primitive. Laminar stamens occur in the
Nymphaeaceae, Austrobaileyaceae, Himantandraceae, and Degeneriaceae
(Canright, 1952). The stamens in the flower of I. floridanum are
la m in a r.
Those stamens with a vascular supply similar to alleged pri
mitive leaves are similarly interpreted as primitive. The 3-trace
condition in stamens is common in the Magnoliaceae, Winteraceae,
and Nymphaeaceae. The 2-trace condition is present in Austrobaileya
and a few Nymphaeaceae. Presence of a single trace, as occurs in
most angiosperms is considered an advanced condition. In Illicium
floridanum, stamens are supplied by 1 trace.
A reduction-modification series is discernable from the laminar
stamen with 4 moderately sunken sporangia, a 3-trace vascular supply,
and an appreciable amount of sterile tissue, to that of the alleged
advanced stamen. Changes involve loss of sterile lamina laterally
to and between sporangial pairs, sim plification of the vasculature,
and the reduction or loss of the sterile tip of the stamen. The
stamen thus produced would have an anther attached distally to a
well-defined filament. A change in the length of the dehiscence
zone of the anther or in the orientation of the attachment of the
sporangial pairs may also occur. In certain dicot and monocot families,
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the intersporangial wall may break down early, resulting in anthers
with 2 Instead of the usual 4 sporogenous locules.
Stamen initiation may be similar to that of the perianth
(Tepfer, 1953) or stamens may have a deeper origin than that of
the perianth and thus be considered axial structures (Satina and
Blakeslee, 1941). In floridanum, the initiation of stamen primordia,
though originating in the Tg layer, is augmented by deeper dividing
cells. After initiation, the stamens exhibit apical growth of short
duration, augmented by intercalary growth. Stamens with flattened
filaments usually show differential marginal growth (Tepfer, 1953).
The filaments of the stamens of II. floridanum widen by generalized
cell division, with no marginal and submarginal in itials observed.
The Nature of the Carpel
The classical concept of the carpel considers it as a leaf-like
structure (Arber, 1937; Bailey and Swamy, 1951; Troll, 1939). Folding
and fusion of carpel margins and unions among carpels have produced
subsequently a variety of carpel types.
Bailey and Swamy (1951) advanced what they consider the
salient trends of carpel specialization as it possibly evolved from
a primitively conduplicate condition. Drimys piperita Hook, f.,
a member of the Tasmannia section, is considered by both Bailey and
Nast (1943) and Bailey and Swamy (1951) to exhibit the mast primitive
group of carpel characters: a conduplicate, unsealed, styleless
condition with extensive stigmatic crests and laminar placentation.
These authors believe that specializations followed: 1) restricted
or extended growth of the adaxial or abaxial carpellary surfaces,
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2) closure of the conduplicate carpel by fusions along the ventral
surfaces, 3) modifications of the stigmatic crests, the conduplicate
style, and the internal glandular surfaces, 4) various forms of
carpel fusions.
Puri (1961) disagreed with various aspects of the conduplicate
carpel theory and asked for reappraisal of several of its contentions.
He suggested that what had been formerly referred to as the ventral
surfaces of the carpel, were, in fact, its "lateral faces". He
further asserted that these "lateral faces", and not the ventral
surfaces, were juxtaposed in their final "folded" form by marginal
involution. As further demonstration, he stated that the orientation
of the ventral carpellary bundles and the funiculus suggested marginal
and not laminar placentation. In Illicium floridanum, the carpel is
conduplicate, with no evidence of marginal elaboration as suggested by
Puri. The ovule is borne in a median axillary position at the base of
the carpel, bordered by the carpellary margins. This highly unusual
placentation has been reported for Ochna by Sattler (personal communica
tion) and for some palm genera by Uhl (personal communication). The
ovule is supplied by branches from the dorsal, ovular and ventral
strands. During carpel development, the adaxially appressed carpel
margins are built up, but do not fuse.
Wilson (1942), in discussing the "telome" theory, considered
the carpel to be formed by the fusion of the distal branchlets of a
determinate branch system resulting in the formation of a laminar
structure. Melville (1962) interprets the carpel as being derived
from a leaf-like structure that bore a fertile appendage. During the
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course of evolution, the leaf folded, enclosing the fertile branch.
M elville's theory would also explain the formation of superior ovaries
by an infolding of the blade of the gonophyll with the resultant
covering of the ovuliferous appendages. Corner (1963) in contesting
M elville's theory, suggested that carpel evolution could be explained
better by the already existing classical concept. The axillary placen
tation of the solitary ovule per carpel in Illicium floridanum might
be used to support M elville's theory; however, the ovular primordiura
is clearly initiated within the carpel area on the apical flank,
inside the carpel wings.
To some researchers (Baum, 1952; Baum-Leinfellner, 1953;
Leinfellner, 1950) certain carpels develop like a peltate leaf, i.e.,
a leaf whose stalk is attached to the base of the blade. The carpel
of I. floridanum shows no evidence of peltation, unlike many other
putatively primitive carpels.
The Apical Residuum
In Illicium floridanum, an apical residuum persists, after
the initiation of the carpels and continues further development.
It loses the tunica-corpus configuration and heightens by activity of
a plate meristem over the surface and an intercalary meristem just
below the apical residuum in the receptacle. Keng (1965) has outlined
drawings of 2 flowers at anthesis, in longitudinal section, but makes
no mention of what appears to be an apical residuum between the carpel
bases. In certain species of Helleborus and Vinca major (Gregoire,
1938) with fewer than 5 carpels, there is no receptacle remaining at
the center after the carpels are initiated; i.e., the carpels are fused
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basally. Flowers such as Butomees and Sedum with more than 5 free
carpels, have some apical residuum remaining after carpel initiation.
In Nymphaea caerulea (Gregoire, 1938) the apical residuum forms a
large central swelling, or knob. It has only a 2-cell-deep meristematic
mantle, with sparse divisions throughout the tissue adding to the
body of the structure. The bulge becomes rapidly parenchymatous.
A similar structure is present in the flower of several other
species of Nymphaea (Moseley, 1961). Moseley states that in N.
odorata forma rubra, after the initiation of the sepals and the
first petals, the meristematic activity of the apex proper diminishes,
and meristematic activity is shifted to a subapical ring region on
which stamens and carpels form. The remains of the floral apical
meristem elongate and are eventually constricted at its base. Moseley
suggests that the central mound heightens by intercalary growth below
its base during the later development of the flower. Illicium
floridanum flowers also have an intercalary meristem in this position,
which causes the central papillate residuum to heighten. In Nymphaea
odorata, the central region eventually forms a mound-shaped structure
found at the center of the stigmatic cup of the mature flower.
In Nuphar (Moseley, 1971), the floral apex, after initiation of
the stamens and carpels, changes its apical configuration from a
mantle-core type to a plate meristem and a peripheral disc marginal
meristem. The plate meristem forms the ventral area, stylar canal,
and locular carpellary regions. The peripheral disc marginal meristem
forms the outer ovary wall. This pattern of development resembles that
of Illicium floridanum in persistence of the residuum and alternation
of its behavior, although the final results are different.
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The flowers of Nuphar and Nymphaea described by Moseley approach
most closely to the Illicium flower in persistence of an apical
residuum. However, as relatively few flowers have been investigated
in detail through ontogeny, it is perhaps premature to assume that the
behavior of the persistent apical residuum in Illicium floridanum is
u n u su al.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LITERATURE CITED
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Bailey, I. W. 1949. Origin of the angiosperms: need for a broadened outlook. J. Arn. Arbor. 30:64-70.
Bailey, I. W. and C. G. Nast. 1943. The comparative morphology of the Winteraceae II. Carpels. J. Arnold Arb. 24:472-481.
______. 1945. The comparative morphology of the W in teraceae V II. Summary and C o n clu sio n s. J . A rnold Arb. 26: 37-47.
______. 1948. Morphology and relationships of Illicium . Schizandra, and Kadsura. J. Arnold Arb. 29: 77-89.
Bailey, I. W. and B. G. L. Swamy. 1951. The conduplicate carpel of dicotyledons and its initial trends of specialization. Amer. J. Bot. 38:373-379.
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l.ierhorst, D. W. 1971. Morphology of Vascular Plants. Macmillan, New Y ork.
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Corner, E. J. H. 1963. A criticism of the gonophyll theory of the flower. Phytomorphology 13:290-292.
Dengler, N. G. 1972. Ontogeny of the vegetative and floral apex of Calycanthus occidentalis. Can. J. Bot. 50:1349-1356.
Eames, A. J. 1929. The role of floral anatomy in the determination of angiosperm phylogeny. Proc. Int. Cong. Plant Sci., Ithaca, 1926. Vol. 1:423-427.
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* Leinfellner, W. 1950. Der Bauplan des synkarpen Gynoceums. Osterr. Bot. Zeitschr. 97:403-436.
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*Linnaeus, C. 1759. Systema Naturae, Tenth Edition.
Melville, R. 1962. A new theory of the angiosperm flower. I. The gynoecium. Kew Bull. 16:1-50.
______. 1963. A new theory of the angiosperm flower. II. The androecium. Kew Bull. 17:1-63.
Moeliono, B. M. 1970. Cauline or carpellary placentation among dicotyledons. Vols. 1, 2. Van Gorcum Press, Assen, The Netherlands.
Moseley, M. F. 1958. Morphological studies of the Nymphaeaceae. I. The nature of the stamens. Phytomorph. 8:1-29.
______. 1961. Morphological studies of the Nymphaeaceae. II. The flower of Nymphaea. Bot. Gaz. 122:233-259.
______. 1971. Morphological studies of Nymphaeaceae. VI. Development of flower of Nuphar. Phytomorph. 21:253-283.
Philipson, W. R. 1946. Studies in the development of the inflorescence. I. The capitulum of Beilis perennis. Ann. Bot., n. s., 10: 257-270.
Plantefol, L. 1948. L'ontogenie de la fleur. Ann. des. Sci. Nat., Bot. et Biol. Veg. ser., 11, 9:35-186.
Puri, V. 1961. The classical concept of the angiosperm carpel: a reassessment. J. Indian Bot. Soc. 40:511-524.
Rehder, A. 1940. Manual of Cultivated Trees and Shrubs. Wiley, New York.
Satina, S., and A. F. Blakeslee. 1941. Periclinal chimeras in Datura stramonium in relation to development of leaf and flower. Amer. J. Bot. 28:862-871.
Schlotterbeck, J. 0. and C. R. Echler. 1901. The structure and development of the fruit of Illicium floridanum. Proc. Am. Pharm. Assoc. 49:585-589. Pharm. Arch. 4:201-205.
Smith, A. C. 1947. The families Illiciaceae and Schisandraceae. Sargentia 7:1-224.
Stone, D. E. and J. L. Freeman. 1968. Cytotaxonomy of Illicium floridanum and I. parviflorum (Illiciaceae). Jour. Arnold Arb. 49:41-51.
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Tepfer, S. S. 1953. Floral anatomy and ontogeny in Aquilegia formosa var. truncata and Ranunculus repens. Univ. Calif. Publ. Bot. 25:513-648.
Thomas, H. H. 1936. Paleobotany and the origin of the angiosperms. Bot. Rev. 2:397-418.
ti *Troll, W. 1954. Praktische Einfuhrung in die Pflanzenmorphologie I , I I . J e n a .
Tucker, S. C. 1959. Ontogeny of the inflorescence and the flower of Drimys winteri var. chilensis. Calif. Univ. Pubis. Bot. 30:257- 336.
Wilson, C. and T. Just. 1939. The morphology of the flower. Bot. Rev. 5:97-131.
Wilson, C. 1942. The telome theory and the origin of the stamen. Amer. J. Bot. 29:759-764.
Wood, C. E. 1958. The genera of the woody Ranales in the south eastern United States. J. Arnold Arb. 39:296-346.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PLATE LEGENDS
E ig . 1 Habitat picture of Illicium floridanum Ellis, the Star Anise. These shrubs flower during March and April in L o u isia n a .
F ig . 2 An individual flower at anthesis. Note variation in tepal size and shape. X 0.4
F ig . 3 . Vegetative shoots of the Star Anise, photographed in March. X 0.25
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 4. A flowering shoot of Illicium floridanum photographed in March. X 0.24.
Fig. 5. A vegetative shoot of Illicium floridanum photographed in March. X 0.27
Fig. 6. The vasculature of the cleared and stained receptacle of a flower at anthesis. X 12
Fig. 7. A maturing fruit photographed in July. X 0.38
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 8. Diagram of an inflorescence with 6 bracts helically arranged in clockwise direction. Represented in the axils of the 5 inner bracts are single flowers. Each flower is subtended by 6 bracteoles arranged in a clockwise helix. Bracteoles and flowers are not la b e lle d . 1 = oldest bract; 2, 3, 4, 5, 6, = successively younger bract-subtended flowers.
Fig. 9. Diagram of a flower in the axil of a bract. The flower is subtended by 6 bracteoles.
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 10. Transection of the flower at the level of the 13 carpels. The large apical residuum at center is surrounded by 13 conduplicate carpels. The approximately 34 stamens are helically arranged; the numerous flattened tepals lie to the outside. X 30
Fig. 11. Tepals from 1 flower arranged in presumptive developmental sequence from oldest at left to youngest at right. X 0.8
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mm
■i' i i t i M
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig . 12 and 13 . A vegetative apex in median longitudinal section. Apical configuration is tunica-corpus. The periclinal division (at arrow) in the subsurface layer high on the right flank is the initiatory site of s le a f primordium. The vegetative apex remains lcw-convex in outline throughout leaf initiation. Fig. 12, X 160; Fig. 13, X 440
F ig . 14 A young floral bud in longitudinal section. A portion of the enclosing bract is seen in the upper left and right sides. Surrounding the individual flower are portions of subtending bracteoles. The youngest appendage on either flank of the apex is a tepal. X. 100
F ig . 15 . A floral apical meristem in median longitudinal section. The configuration is tunica-corpus. The appendages on the left and right side of the apex are tepals. Note the periclinal division in the subsurface layer high on the right side of the apex; this is not involved in appendage initiation. X 200
F ig . 16 . A floral meristem in non-median longitudins.1 section, to show young tepal primordia on the left end right flanks of the apex. X 200
F ig . 17 . A tepal primordium 80p high in median longitudinal section. Note the subapical initial (at arrow) and procarabial strand. A stamen protrudes above the tepal. X 400
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F ig . 18. A floral apex in median longitudinal section. The periclinal division (at arrow) in the subsurface layer on the right flank is the initiatory site of a tepal. X 200
F ig . 19. A floral apex in transverse section, with the floral meristem at center. The appendages are tepals of differing ages. Note the beginning of marginal and submarginal activity in the upper left tepal (at arrow). X 100
F ig . 20. A flower, in transverse section. The floral meristem is at the bottom. The most recently formed protuber ances are the first formed stamens. The flattened outermost structures are tepals of differing ages. The outermost tepals show extensive cell maturation. In a young tepal (at arrow) the cells of the ground meristem on the abaxial side soon appear vacuolate and stain differently than the remaining cells of the tepal. X 150
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 21-23. Tepals in transverse section.
F ig . 21. Marginal and submarginal activity has produced an ellipsoid transverse section. X 50
F ig . 22. Marginal and submarginal activity has produced a crescent shape in transverse section. The margins of the outer tepals (at M) have begun to narrow due to the extended activity of marginal initials. X 25
F ig . 23. Note (at M) the extended activity of the marginal initials in two of i:he tepal margins. X 25
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 24. Floral bud in transverse section. Note (at. arrows) the tepals of differing ages and the degree, of marginal activity that has produced a narrow 2-cell- layer margin. X 100
Fig. 25. A maturing tepal in transverse section. Colls are vacuolate. Note the numerous dark-staining pigmented cells. X 50
Fig. 26. A floral apex in longitudinal section. The initiatory site of a stamen (at £3) on the lower right flank is non-median and younger than the site (at S) on the lower left flank. Tepals stand centrifugally to each stamen site. The remaining appendages are older tepals. X 250
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 27. A floral apex, in median longitudinal section. The initiatory site of a stamen of the second or youngest series is at arrow at left. X 300
Fig. 28. A floral apex in longitudinal section. Th€; initiatory sites (S) are stamens of the second series. X 250
Fig. 29. Young stamen primordia (S) of the outer or first series in transverse section. All other appendages are tepals (T). The receptacle is at the bottom. X 200
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F ig . 30. The floral receptacle and stamen primordia in transverse section. Appendages at upper right and lower left are te p a ls . X 100
F ig . 31 and 32. Young stamen primordia (S) of the first series in longitudinal section. T = tepal. Fig. 31, X 200; Fig. 32, X 250
F ig . 33. A floral apex and young stamen primordium (S) of the first series in longitudinal section. A subapical initial. The tepals (T) are at right. X 250
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Fig. 34. A floral bud, in longitudinal section. The first appendage to the right of the apical residuum is a developing carpel (C). The second and third appendages are stamens (S) of the second and first series, respectively. The large curved appendage at far right and top is a tepal. Note the adaxia l. curvature of the developing stamens, in contrast to the carpel. Procambium is present at the base of the outer stamen. X 100
F ig . 35 and 36 Stamen primordia (S) of the first and second stamen series in longitudinal section. Note the presence of procambium at the base of the primordium. Fig. 35, X 350; Fig. 36, X 450
Fig. 37. A floral bud in longitudinal section. A common sympodium is supplying s. tepal (T) and a stamen (£3) of the second series. X 100
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75
Fig. 38. A mature stamen at anthesis in March. A cleared preparation, retouched to show the outline of the stam en. X 16
Fig. 39. Young stamen primordia in transverse section. No marginal or submarginal initials are present. X 300
Fig. 40. A mature stamen filament in transverse section, showing a single vascular strand. X 25
Fig. 41. A 4-sporangiate, introrsely lateral anther at anthesis in transverse section. X 150
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 42. Stamens of the first and second stamen series in longitudinal section. The stamens are about 400ji high. Note the sporogenous tissue and the xylem differentiating at the base. X 150
Fig. 43-46. Developing anthesis in transverse section.
Fig. 43. Sporogenous cells (at arrows) have recently form ed. X 200
Fig. 44. The single sporogenous cell (at arrow), at this level, is surrounded by a uniseriate parietal layer. X 300
Fig. 45. The sporogenous cells are surrounded by a multi layered parietal tissue and endosporum (E). The tapetum forms from the inner cell layer of the p a r i e t a l t i s s u e . X 250
Fig. 46. Note the clustered sporogenous cells and the maturing anther wall. E = endosporum. X 225
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 47-50. Microsporogenesis in transverse section of anthers. The endothecium (E) is indicated in each.
F ig . 47 and 48. The sporogenous cells are separating prior to meiosis. Fig. 47, X 250; Fig. 48, X 30C
Fig. 49. The dyad is formed at the first meiotic division. Note the layers of the maturing anther v/all: a single epidermal layer, an endothelial layer (E), 1 to several middle layers in the process of being crushed, and a tapetum. X 400
Fig. 50. Tetrads form after the second meiotic division. X 300
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 51 and 52. Microsporogenesis, in anthers in transverse section. Prior to separation, the cytoplasm shrinks from the walls of the tetrad cells. Note the maturing anther wall. The greatly collapsed appearance is, in part, an artifact of preparation. E = endothecium. X 275
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig . 53. Carpel initiation (C) on the floral apical meristem in longitudinal section. The arrow indicates two
periclinal divisions in the T 2 . A stamen primordium (£) of the second series stands at left. X 600
F ig . 54. A floral apical meristem, stamen (£), and early carpel primordium (C). Note the two periclinal divisions (at arrow) in the subsurface layer on the flank and the adjacent procambium. X 500
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. *J4f#^ ■ + ' m * • «ft.«
* ,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig . 55. The carpel primordium (C) in longitudinal section as it becomes a protuberance. A stamen primordium (£3) of the second stamen series stands at lower right, and tepal (T) at upper right. X 400
F ig . 56. A floral apex in transverse section showing some of the 13 carpel primordia. £> = stamens. X 100
F ig . 57. A carpel primordium (C) in longitudinal section. The subapical initial (at arrow) originates when a carpel is approximately 60p. T = tepal. X 300
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Fig. 58. Young carpel priaisrdium (C) on the flank of the apical residuum. X 250
Fig. 59. Apical residuum flanked by carpels (C) 350j high. X 100
Fig. 60. A floral bud in transverse section. The apical residuum is at the base. The first series of appendages surrounding the residuum are carpels (C) 150-200ji high, with early marginal growth (at arrows). The second series of appendages are stamens (S). X 300
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m m
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 61-63. Conduplicate carpels at different stages of tangential and radial enlargement, sectioned transversely slightly above the ovular region. AD = adaxial. Fig. 61, X 225; Fig. 62, X 100; Fig. 63, X 100
Fig. 64. Carpel and developing ovule (OV) in longitudinal section. A plate meristem (at arrow) builds up the appressed adaxial carpel margins. X 100
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 65-68. Cleared whole carpels stained to show xylera strands. D = dorsal strand; 0 = ovular strand; V = ventral strands; AB = abaxial surface.
F ig . 65 and 66 Carpels at the time of flowering in March. Note the minor branches of both the dorsal strand and the ventral strands. Fig. 65, X 10; Fig. 66, X 17
F ig . 67 and 68 Fruit development in June. Note the adaxial expansion of the carpel at its attachment, the numerous minor branches of the dorsal strand- and ventral strands, and the curving of many of the branches of the dorsal strand to the region of the developing seed. Fig. 67, X 6; Fig. 68. X 13
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93
Fig. 69-72. Developing carpels.
Fig. 69. A carpel primordium (C) about 50ji high in longitudinal section. Note the presence of procambium (at arrow) below the primordium. X 300
Fig. 70. A carpel primordium (C) about 80/j high in longitudinal section. Note the presence of procambium. X 250
Fig. 71. A carpel (C) and developing ovule (OV) in longitudinal section. Xylem differentiates in the dorsal strand of a carpel when the carpel is 300-350;: high. AB = abaxial surface. Arrow indicates xylem. X 200
Fig. 72. A carpel and developing ovule (OV), in longitudinal section. Xylem differentiates in the region of the ovule when the ovule is about 200^ high. X 175
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 73-76. Ovule initiation and early development in longitudinal section. AD = adaxial surface; AB = abaxial surface; C = carpel; OV = ovule.
Fig. 73. Ovule initiation. The ovule (OV) is initiated medianly at the base of the carpel (C). X 200
Fig. 74. Early ovule development. The ovule (OV) is 60ji high. The carpel (C) is 300ji high. X 200
Fig. 75. An ovule primordium (OV) 80/x high. Note the subapical initial (at arrow). The carpel is 350ji high. X 300
Fig. 76. A developing ovule 125 ji high. X 200
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Fig. 77. A carpel and developing ovule (OV) about 200p high in longitudinal section. X 175
F ig . 78 and 79. Carpels and developing ovules in transverse section, at different ages. The appressed carpel margins never fuse through carpel and fruit development. The adaxial carpel margins (at arrows) build up during carpel maturation by derivatives of a plate meristem. Fig. 78, X 150; Fig. 79, X 100
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mm
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig . 80' 83. Young ovules in a section cut transversely through the carpels.
F ig . 80. A recent periclinal division in the subsurface layer has produced an archesporial cell (at arrow). X 400
F ig . 81. Early maturation of the archesporial cell (at top arrow) and the initiation of the first and second integuments. The inner integument forms first and is protodermal in origin. The second integument forms by periclinal divisions in the subsurface layer behind the inner integuments and enciccles the ovule like a cap. The division (at lower arrow) is part of the rim of the outer integument. X 400
F ig . 82. Ovule with megaspore mother cell (at arrow). The inner integument only is in the plane of section. X 325
F ig . 83. Longitudinal section through the adaxial rim of the outer integument. X 350
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101
Fig. 84-86. Megasporogenesis in longitudinal section, oi = outer integument; ii = inner integument.
Fig. 84. The megaspore mother cell in the ovule is cut sagittally. Note the parietal cell (at arrow) and the megaspore cell positioned to its left. The micropylar canal is observed because of the plane of section through the inner integuments. X 275
Fig. 85. The 2-cell stage in sagittal longitudinal section. The arrow indicates one of the 2 cells. X 250
Fig. 86. The 4-megaspore stage showing 3 of the 4 megaspores (at arrow). A sagittal longitudinal section. The micropylar megaspore is out of the plane of section. X 400
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103
F ig . 87. The embryo sac in sagittal longitudinal section. The central nucleus (CN) is in the plane of section. At the base of the embryo sac is the hypostasc. (Ip with its darkly staining cells. X 100
F ig . 88. Part of the egg apparatus (EA) in the embryo sac in sagittal longitudinal section. X 250
F ig . 89. The zygote (Z) in the embryo sac in sagittal longitudinal section. X 100
F ig . 90. An early stage in endosperm (EN) formation in the embryo sac in sagittal longitudinal section. X 100
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F ig . 91 93. Development of the seed coat in longitudinal s e c tio n .
F ig . 91. The outer integument (between upper pair of arrows) has 5 layers, the inner integument (between lower p a i r o f arrow s) has 3 c e l l la y e r s . X 225
F ig . 92. The 4 inner layers of the outer seed coat are darkly stained. The non-pigmented cells in the fifth (outermost) layer are elongated anticlinally. The interface between inner and outer seed coat is shown at the arrow. X 400
F ig . 93. Part of the matur seed coat. The anticlinally elongated cells of the outermost layer remain non-pigmented with heavily thickened walls. The first and second layers of the 3-layered inner seed coat are crushed at seed coat maturity. The boundary between the inner and outer seed coats
is at the arrow. X 3 5 0
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107
Fig. 94. Fruit development. Whole mounts. The expansion of the carpels during fru it development is shown from a, at flowering in March, to m, at dehiscence of the seeds in October, a, b (March); c, d (April); e, f (May); £, h (June); jL, j, (July); k (September); _1, m (October). X 0.75
Fig. 95. Receptacle and part of one maturing follicle, in cleared preparation. As the receptacle enlarges during fruit development there is an expansion of intervascular areas. The base of the apical residuum is at the arrow . D = dorsal b u n d le ;0 ~ o v u la r b u n d le; V = v e n tra l b u n d le . X 32
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Fig. 96-98. Development of the apical residuum (AR) in longitudinal section.
F ig . 96. The tunica-corpus configuration is lost, and the flanks of the residuum show some heightening. Many cells of the three outer layers are beginning to divide periclinally. X 200
F ig . 97 and 98. An apical residuum at: 2 different levels in the same flower in transverse section, surrounded by carpels. X 150
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 99-101. The developing apical residuum in median longitudinal section.
F ig . 99. The apical residuum (AR) is 500)i wide and 300yi high. Note the cell files along the periphery. OV = ovule. X 200
F ig . 100. Note the cell enlargement and differentiation in the central region of the apical residuum CAR). OV = ovule. X 275
F ig. 101. Note the differentiating cells near the summit of the apical residuum (AR) subtended by s till meristematic cells at the base. The carpel (C) and ovule (OV) are at right. AD = adaxial carpel surface (non-median). X 200
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Fig. 102 and 103. Two examples of differentiating apical residuum (AR). Note the differentiation of the summital cells, with a basal intercalary meristem (Ip. Fig. 102, X 125; Fig. 103, X 175
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115
Fig. 104. Part of a floral receptacle with a single carpel in longitudinal section. The summit of the apical residuum (AR) is being sloughed off, while the basal intercalary meristem is producing derivatives from below. The section is median, except for the developing seed. Arrow indicates the plate meristem building up the adaxial side of the carpel. AB = abaxial. X 20
Fig. 105. The collapsing tannin-filled cells of the apical residuum (AR) in the process of being sloughedoff, in longitudinal section. X 100
Fig. 106. The intercalary meristem, at the base of the residuum, after the tannin-filled cells of the apical residuum have sloughed off. C = carpel. X 150
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Richard Earl Robertson was born in Omaha, Nebraska, March 5,
1941; son of Howard E, Robertson and Thelma R. Robertson. He attended
public schools in Omaha, Nebraska and graduated from South High School
in 1958.
He entered the College of the Ozarks, Clarksville, Arkansas,
in 1961, and received the Bachelor of Science degree in biology in
June, 1965.
He entered graduate school at Northeast Louisiana University,
Monroe, Louisiana, in 1965, and received the Master of Science degree
in biology in January, 1968.
He continued graduate studies at Louisiana State University,
Baton Rouge, Louisiana, where he is presently a candidate for the
Doctor of Philosophy degree in botany.
He is married to Patricia Peirce Robertson, and they have one
child, Stephanie Dawn, age seven.
117
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. EXAMINATION AND THESIS REPORT
Candidate: Richard Earl Robertson
Major Field: Botany
Title of Thesis: An O n to g en etic Study o f I llic iu n i F loridanum E l l i s W ith Emphasis on Stamen and Carpel Development. Approved:
J.CL. Major Professor and Chairman
Dean of the Graduate School
EXAMINING COMMITTEE:
liJ lO H c L * ------
Date of Examination:
______July 19, 1973
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