BLUMEA 23 (1976) 189—201

The vascular pattern in the flower of some

Mesembryanthemaceae:

Aptenia cordifolia and Dorotheanthusbellidiformis.

The effect ofan ontogenetical shifting on the vascular

pattern and vascular conservatism

C. van der Meulen-Bruijns

Afdeling Plantensystematiek, Biologisch Centrum Harcn, Rijksunivcrsiteit Groningen, Netherlands.

Contents

I. Introduction 189

2. Materials and Methods 190

2.1. Complete flowers 190

2.2. Sections offlowers 191

3. Observations 191

3.1. Aptenia cordifolia 191

3.2. Dorotheanthus bellidiformis 192

4. Discussion 193

4.1. Comparison between the vascular patterns of Aptenia cordifolia and Dorotheanthus bellidi-

formis 193

4.2. Comparison with observations of Ihlenfeldt 198

4.3. Comparison with other Centrospermae 199

4.4. The interpretation of the inferior ovary 199

4.5. Conclusions 200

5. References 201

Summary

The vascular in the flower various of of and Dorotheanthus 1. pattern at stages maturity Aptenia cordifolia bellidiformis is examined.

The vascular ofDorotheanthus has been with that of Dorotheanthus 2. pattern compared Aptenia: typologically, is derived from Aptenia.

3. The vascular pattern of Apteniahas been compared with the observations ofIhlenfeldt: the differences are due of different methods. probably to the use

4. The vascular pattern in the ‘ovary wall’ ofAptenia has been compared with that in the outer floral whorls of Melandrium rubrum the decision which ofinferior (Caryophyllaceae):: itis necessary to postpone as to type in ovary is present Aptenia and Dorotheanthus untill more evidence is available.

1. Introduction

The Mesembryanthemaceae (order Centrospermae) are indigenous to South Africa and show more or less succulence. The flowers are characterized by (Ihlenfeldt, Schwantes

& —6 Straka, 1962): 1) a calyx with 4 , mostly of unequal size; 2) several whorls of

and semi-inferior petaloid ; 3) a plurilocular, to inferior, syncarpous

of attached to the ovary, compounded 3—23 carpels; 4) mostly many ovules, placenta by and a very long funicle; 5) characteristic loculicide, hygrochastic capsules. VOL. 190 BLUMEA 23, No. I, 1976

The sub-families of the Mesembryanthemaceae used to be classified in the family

(=Ficoidaceae) (e.g. Eckardt, 1964). However, according to Ihlenfeldt & Straka (1961), they have to be treated as a separate family.

The Mesembryanthemaceae can be dividedinto two groups according to the placentation, and into four subfamilies, as follows: group A: axile placentation.

1. Mesembryanthemoideae sensu Ihl., Schw. et Str. (syn. with Aptenioideae Schwant.).

2. Hymenogynoideae Schwant.

3. Caryotophoroideae Ihl., Schw. et Str.

basal to placentation. group B: pseudo-parietal

4. Ruschioideae Schwant.

The members of to be than those of group A are supposed more primitive group B.

both are identical, and have axile (Ihlenfeldt, Very young stages of types placentation the of the Ruschioideae the shifts from 1961). In genera placentation ontogenetically This of axile to basal or parietal (already noted by Huber, 1924). shifting is the result

in in changes in relative growth rates the ovary. These changes relative growth rates have

known for and Buxbaum illustrated them in the Mesem- been a very long time, (1951) This the basis of the bryanthemaceae (his fig. 27). means that, on carpel concept, it is in- describe Ruschioideae. should be correct to use the term parietal to placentation in the It but still called interpreted as being axile, is pseudo-parietal.

the In a study on Mesembryanthemaceae, Ihlenfeldt (1961) made a comparison between the vascular patterns in ovaries with diverse types ofplacentation. Although in his study vascular eluci- some very complicated patterns (e.g. Dorotheanthus) were not completely

Ihlenfeldt concluded that the vascular be reduced a dated, various patterns can to common groundplan; and that, with regard to the vascular pattern, the subfamily Ruschioideae derived should be considered to be more than the subfamily Mesemhryanthemoideae.

On account of the foregoing it was decided to examine the effect of ontogenetical

vascularisation. that the vascular in a flower with shifting on For purpose pattern pseudo-

will be with the vascular a flower with axile parietal placentation compared pattern in placentation. As an example of the latter the flower of Aptenia cordifolia (L./) Schwant.

(subfamily Mesembryanthemoideae) will be examined. Preparatory studies demonstrated, of Dorotheanthus than from that the vascular pattern is much more complicated appears of the study of Ihlenfeldt (1961). So as an example the group with pseudo-parietal placen-

tation the flower of Dorotheanthus bellidiformis (Burm./) N. E. Br. (subfamily Ruschioideae) will be examined.

2. MATERIALS AND METHODS

From , cultivated in Hortus de Wolf, Haren (Gr.), flowers at various stages of

in maturity (buds, flowers, and fruits) were collected, and preserved ethyl-alcohol 70% FPA Examination carried flowers and sections of flowers. or 70%. was out on complete on

2.1. Complete flowers. bleached with and the elements the 1. Preserved specimens were NaOH lignified in vascular bundles stained with basic fuchsin (Fuchs, 1963).

2. Preserved specimens were bleached with lactic acid and the vascular bundles (phloem and xylem) stained with lacmoid (Aloni & Sachs, 1973). C. van der Meulen-Bruijns: The flower of some Mesembryanthemaceae 191

2.2. Sections of flowers.

in Preserved specimens were embedded paraplast according to the standard technique,

via TBA-dehydration. The thickness of the transverse and sections longitudinal was 7 fx.

The sections were stained with astra blue-auramine-safranine (Maasz & Vagas, 1963).

3. OBSERVATIONS

is it 3.1. Aptenia cordifolia tetramerous, has sepals of unequal size, two bigger and two smaller ones. The ovary, with four locules and four complete septa, is inferior in the the fruit axile. young flower, in ripened it is semi-inferior. Placentation is

Vascular architecture and 3.1.1. (fig. 1 3).

In the pedicel four vascular bundles, called primary bundles, occur in one circle (A,

ascend in wall 1 in between the Two of them fig. 1-1). They the ovary ) septa. do not branch and supply the central portions of the two bigger sepals. The other two bundles

A give off two bundles each (B, fig. 1-2), and ascend towards the smaller sepals.

The four bundles B are situated inside thecircle ofprimary bundles, and give off three bundles each the floral base and The bundles and in (Ci C2, fig. 1-3; B', fig. 1-4). Ci C2 form commissure C The bundles B and B' ascend in the wall in a (fig. 1-3). ovary the

radii. On the level of the rim the bundles B form commissure septal hypanthium split up, a The with the bundles A, and supply the lateral portions of thesepals (fig. 1-9, 10). bundles

B' form which rise the staminodes a commissure, gives to many bundles, supplying and

stamens (fig. 1-8, 9, 10).

Commissure C gives rise to four bundles which ascend in the radii of the bundles A

(Ci,2, fig. 1-4). Higher up the bundles Ci,2 split into three bundles each (fig. 1-8), the into central one (C3) enters finally the style. The styles are situated in between the septa,

with one vascular bundle each (C3, fig. 1-10). The other two bundles, branching several form the roofof times, a plexus in the ovarian cavity (Ci,2, fig. 1-9). This plexus gives rise in in lower to some bundles, descending theseptal radii, ending blindly the part of the

ovary (C', fig. 1-7).

Commissure C gives rise to another eight bundles (D, fig. 1-4). The two bundles D

at both sides ofone bundle B fuse and run centripetally in the septal radius into the central

column (fig. 1-4,5). In the central columnthese four bundles D ascend, still in the septal

off branches in the half of the radii (fig. 1-6), giving some upper ovary (E, fig. 1-7)

supplying the placentae. So each bundle D gives off some bundles E into the placentae in

the two adjacent locules. (A placenta is a narrow strip of tissue on the central column, the the locule. There of ovules borders projecting into are two rows on it.) Furthermore, the there each in placenta are two conspicuous parallel bundles, that are joined to other branches. The bundles by fusion or are connected by small placentary are connected with

the bundles E (fig. 1-7). The vascular supply in the funicles is derived from the placentary

in the central column the bundles D unite bundles. High up split and with the placentary bundles.

Generally, there is not much variation in the vascular architecture in various flowers.

it is in A representative pattern can thereforebeconstructed; represented a three-dimensional model in fig. 3.

Since is in wall' and *) there no unanimity the definition of the terms 'ovary 'hypanthium'(see e.g. Eames, Merxmiiller and Puri, in the the 1961; Leins, 1972; Leins, Sattler, 1972; 1951, 1952), present study term

'ovary wall' is used to indicate the total wall outside the ovarian cavity. BLUMEA VOL. No. 192 23, I, 1976

of the vascular bundles. 3-1.2. Orientation of is turned the In the centripetally running part bundle D, xylem downwards, cen-

orientated The bundles are halfinverted. the bundles trally ascending part is normally. E In towards each E, innervating one placenta, the xylem strands are turned other. The

bundles in the placenta seem to be amphicribral. The remaining bundles A, B, and C

have normal orientation.

Dorotheanthus has of The inferior 3.2. bellidiformis is pentamerous, it sepals equal size. has five locules and five Placentation ovary complete septa. is pseudo-parietal.

Vascular architecture and 3.2.1. (fig. 2 4). vascular called and In the pedicel ten bundles, primary bundles, occur in one circle (A B, A in in fig. 2-1). The bundles ascend the ovary wall between the septa, without branching, and supply the central portions of the sepals. the sometimes In floral base, or at a higher level, the bundles B give off two bundles B in in each (Ci and C2, fig. 2-2, 3, 4, 5). Then the bundles ascend the ovary wall the

offanother bundle in the halfof the On septal radii, giving upper ovary (B', fig. 2-7).

the level of the hypanthium rim the bundles B split (fig. 2-7), form a commissure with

the bundles A (fig. 2-8, 9), and supply the lateral portions of the sepals. The bundles B'

form commissure which rise the staminodes and a gives to many bundles, supplying stamens

(fig. 2-9, 10).

The bundles Ci and C2 ascend, changing their positions from the septal radius to the and he radius of bundle A, come to inside the circle of ten primary bundles A and B (fig. The bundles the roof 2-6, 7). Ci and C2 branch many times and form a plexus in of the

This rise the bundles. The ovarian cavity (Ci,2, fig- 2-8, 9). plexus gives to stylar styles are

situated between the with two vascular bundles each In the septa, (Ci, 2, fig. 2-10). upper and off halfof the ovary the bundles Ci C2 give one bundle each (D, fig. 2-6, 7). and The bundles D make a sharp reverse turn. Two bundles D fuse in the septal radius descend the floral base these bundles (fig. 2-5, 6). In compound D run centripetally into central and half The the column (fig. 2-2, 3), ascend, end blindly way up the ovary. of bundle off bundles which branch descending part D gives various (E, fig. 2-5, 6, 7) and connect with the bundles in the placentae in the two adjacent locules. In the placenta

there is a random network of vascular bundles, giving rise to the bundles in the funicles.

In columnanother five bundles the the central occur, alternating with septa (F, fig. 2-4,

5,6). Between the bundles D and F there are several connecting branches, so together diey the build a cylindrical vascular plexus. The bundles F end blindly at a level half way up

in ovary; the floral base they run horizontally, supplying the basal portions of the placentae

over the lower of the central the bottom (F, fig. 2-3, 4). (A placenta is spread part column, is of the ovary, and the ovary wall, so forming a triangle. The horizontal portion convex, because of in the bottom of the locule. There ovules of the presence a thickening are many attached to the placenta in an undefinedpattern.)

The details of the vascular architecture be not in different can very variable, only flowers, but in of the with the even different compartments same ovary, particularly regard to and bundles D, E, and F. Even so a fairly representative pattern can be constructed, it is in modelin represented a three-dimensional fig. 4.

of the vascular bundles. 3.2.2. Orientation bundles in In the roof of the ovarian cavity the Ci,2 are half-inverted: the bundles

supplying the roof of one locule, the xylem strands are turned towards each other. The C. van der Meulen-Bruijns: The flower of some Mesembryanthemaceae 193

in in D two bundles the style are half-inverted the same way. The descending part ofbundle the the turned the is inverted, in centripetally running part xylem is downwards, centrally

ascending part is orientated normally. The orientationofthe bundles in the placenta could

not be defined.The remaining bundles A, B, Ci, and C2 have normal orientation.

4. DISCUSSION

Examination the in of flowers, prepared according to method described 2.1.1., makes it the the possible to construct a three-dimensionalmodel of vascular architecture in flower.

and that A drawbackof this method is that only lignified elements are stained young bundles

visible. This is in the in not yet lignified are not especially important young stages, which, all vascular bundles have this limitation have moreover, not yet developed. However, can its advantages when studying flowers with a very complicated vascular pattern (e.g.

Dorotheanthus because it is in those ), possible, cases, to start by making a very simplified

model based on the juvenile vascularisation and to gradually fill in the details as the older

material is stages are examined. Since, by using method2.1.1., only lignified visible, method has be details of the vascular then 2.1.2. to used to supply more pattern. Even it is possible that the smallest bundles are overlooked, so that thefinal details must be elucidated by means of serial transverse and longitudinal sections. It is not possible, however, to construct a

three-dimensional model of vascularisation on the basis of serial sections alone. In Doro-

for it is sections how main vascular theanthus, example, not clear from many bundles are of bundles. present in the central column because ofthe presence connecting By examining cleared evident that five the radii whole flowers it is quite there are ten bundles, in septal (D) and five alternating with them (F). It is necessary to examine sections to establish the orien-

tation of the bundles.

4-1- Comparison between the vascular patterns of Aptenia cordifolia and Dorotheanthus bellidiformis.

The similarities are as follows: The branches 1. bundles A enter the sepals as their midveins and give offno to the inner floral whorls.

2. The bundlesB supply the lateral portions of the sepals and give off some branches the bundles a. to stamens and staminodes: the B', forming a commissure;

b. the in the roof of the ovarian to ovary wall: the bundles Ci and C2, forming a plexus cavity andsupplying the styles. For the sakeof convenience the complex ofC bundles (the whole complex ofrespectively C1+C2+C3in Aptenia andC1+C2 in Dorothean-

thus) is named the dorsal carpellary bundle, without implicating the classic carpel theory.

3. The bundles D branch offfrom the bundles Ci andC2. Two bundles D fuse in the septal the radius and then give off some branches to the placentae in two adjacent locules.

For the sake of convenience the bundle D is named the commissural ventral carpellary

bundle, again without implicating the classic carpel theory.

The differences are as follows:

bundle Aptenia Dorotheanthus

B branches off from A in the pedicel. is a primary bundle.

B' branches offfrom B in the floralbase. branches off from B on the level of the hypanthium rim. No. 194 BLUMEA VOL. 23, 1, 1976

Some sections, Fig. 1. Aplenia cordifolia. transverse i: pedicel; 10: top. C. van deh Meulen-Bruijns: The flower of some Mesembryanthemaceae 195

Some Fig. 2. Dorotheanthus bellidiformis. transverse sections, i: pedicel; 10: top. 196 BLUMEA VOL. 23, No. 1, 1976

bundle Aptenia Dorotheanthus

and commissure in C Ci C2 form a C Ci and C2, not forming a com- the floral floral base, giving rise to the missure in the base, ascend

bundles the radii the radius ofbundle Ci, 2, ascending in separately in A; of the bundles A;

the bundle the the bundles and the Ci,2 splits in upper Ci C2 unite in of of half the ovary into three: the upper half the ovary and form a the of the central one (C3) supplying style, plexus in the roof ovarian

the other two forming a plexus in cavity, supplying the styles, each

the roofofthe ovarian cavity; from with two vascular bundles.

this plexus some branches C' de-

scend in the septal radii, ending

blindly.

D branch off from Ci and C2 at the branch off from Ci and C2 in the level of the floral half of the base; upper ovary; half unite high up in the central column end blindly way up the central with the placentary bundles. column;

form a cylindrical plexus with the

bundles F in the central column.

E branch little. branch frequently.

the basal F not present. present, supplying por- tions ofthe placenta. of bundles. placentary two conspicuous parallel bundles. a random network

bundles

The shows that the bundles and ascend in from the present study B B' separately, Aptenia

floral base, and in Dorotheanthus from the level of thehypanthium rim. So one is tempted to

think that in Dorotheanthus there is adnation between the bundles B and B'. However, the

shifting of the placentation in Dorotheanthus is the result of differences in relative growth

various his The shows rates in parts of the ovary (Buxbaum, 1951, fig. 27). present study

that:

and branch off from B in the both in and in a. The bundles Ci C2 ovary base, Aptenia Dorotheanthus. b. Thebundles D branch offfrom Ci and C2, in Aptenia abouthalfway between the origin

and the fusion of the bundles Ci and C2, in Dorotheanthus near the fusion of the bundles

Ci and C2.

cannot From this it can be inferred that the fusion of the bundles B and B' in Dorotheanthus

but of wall between be understood as adnation, is the result intercalary growth in the ovary

the origin of the bundles Ci and C2 and the origin of the bundles B'. there is how the bundle F in Dorotheanthus should be inter- At present no evidence as to in preted. It doesn't occur in Aptenia, but contributes to the vascular supply ofthe placenta

Dorotheanthus. Three possibilities can be suggested:

does fact the like a. Bundle F is equivalent to bundle E. Bundle F in supply placenta, E,

but doesn't originate from bundle D, as does E. between b. Bundle F is equivalent to bundleD. In thecentral column there is no difference

in orientation. bundle D the bundles D and F, either in size, or course and However, C. van deh Meulen-Bruijns: The flower ofsome Mcsembryanthemaceae 197

in the Fig. 3. Aptenia cordifolia. 1: Three-dimensional model ofthe vascular architecture flower. 2: Schematic

section the half of the central column. transverse through upper

in Fig. 4. Dorotheanthus bellidiformis. 1: Three-dimensional model of the vascular architecture the flower. section 2: Schematic transverse through the ovary base. 3: Schematic transverse section through the lower half of the ovary. BLUMEA VOL. 23, No. I, 1976 198

bundle branches off from bundle Ci or C2 and is situated in the septal radius, while F

with and alternates with the in has no connections bundle Ci or C2 septa. In fact, the

bottom F bundle D off of the ovary bundle supplies the placenta directly, while gives placental bundles (E).

c. Bundle F is not equivalent to any other vascular bundle. Like the other placental

F is in all of it doesn't vascular bundles (D and E), bundle present stages maturity, so develop secondarily.

further studies other will Probably on some species elucidate this problem.

The results of this study demonstrate that the vascular pattern in the pseudo-parietal

placentation ofDorotheanthus can be interpreted as derived from that in the axile placen-

of a the wall. the examined were not tation Aptenia by shifting in ovary As flowers young

enough, in this study the ontogenetical shifting has not been investigated (e.g. Huber,

1924; Ihlenfeldt, 1961).

4.2. Comparison with observations oflhlenfeldt.

Ihlenfeldt (1961) suggested two types of vascular pattern for the Mesembryanthemaceae. served of the Aptenia as a representative example subfamily Mesembryanthemoideae (syn. dis- with Aptenioideae), Delosperma of the subfamily Ruschioideae. These patterns show several with the results of the similarities in respects present study.

4.2.1. Mesembryanthemoideae: Aptenia.

1. Ihlenfeldt doesn't mention the dorsal carpcllary bundle complex Ci —C2—C3,

the radius bundle 1 'Der ascending in of A (BB) ). He says (p. 43): Dorsalmedianus, der

der offenbar unterdriickt oder an Aussenwand des Fruchtknotens aufsteigen miisste, ist

nur so schwach ausgebildet, dass er sich aus der Vielzahl der kleinen zusatzlichen Gefasse nicht heraushebt.'

of 2. Ihlenfeldt indicates a commissure (K2) between the bundles (L). In his figures trans- situated the verse sections (Abb. 6, fig. 5) this commissure is in the central column, in base. is longitudinal section (Abb. 6, fig. 15) it is situated in the ovary Bundle (L)

is the absorbed in this commissure. In the present study the bundle (L) interpreted as column. The ventral bundle D. This bundle D ascends to the top of the central com-

has been observed the Indeed all bundles start missure (K2) not in present study. E

oft in and form a branching at the same level the central column (fig. 1-7), seem to

commissure.

Ihlenfeldt describes his ventral bundle with 3. carpellary (VM) as alternating a septum.

In his figures of transverse sections (Abb. 6, fig. 6, 7) this bundle is found only in the vascular bundles central column and arises at a point where the placenta with two is

the author did not observe a vascular bundle in the already present. In Aptenia present central with vascular is situated in column alternating a septum. The ventral bundle D

the central column in the septal radius. Ihlenfeldt's bundle (VM) is, in the present the study, interpreted as a bundle E, branching off from the ventral bundleD (L). In

figure of the longitudinal section (Ihlenfeldt, Abb. 6, fig. 15) the bundle (VM) is

found only in the placenta and arises in the floral base. In Aptenia the present author also observed two conspicuous parallel bundles in the placenta, as is indicated in the

transverse sections of Ihlenfeldt. In the present study Ihlenfeldt's bundle (VM) is bundle. interpreted as a placentary

brackets the characters used Ihlenfeldt for the bundles in the !) In are by corresponding present study. The C. van der Meulen-Bruijns: flower of some Mescmbryanthemaceae 199

The present study agreed with Ihlenfeldt's figures of the transverse sections of the his of the doesn't with Mesembryanthemoideae. However, figure longitudinal section agree of the results of the The differences his figures transverse sections, nor with present study. of Ihlenfeldt and the author in interpretation present concerning Aptenia(Mesembryanthe-

moideae) are probably due to the fact that Ihlenfeldt based his study on sections only.

4.2.2. Ruschioideae: Dorotheanthus.

of of A comparison between the vascular pattern Delosperma, as an example the Ruschioideae the of and that of Dorotheanthus the in study Ihlenfeldt, in present study, is made this results not at moment. There are so many differences, both between the of between the Ihlenfeldt and the present author concerning Dorotheanthus, and vascular patterns of the two species, that comparison is impossible without further examination of Delosperma.

with 4.3. Comparison other Centrospermae. Moeliono the basis of his and the illustrations of (1970) concluded, on own study on e.g.

Ihlenfeldt that the of the a vascular (1961), in ovary Mesembryanthemaceae placental pattern is in Before found similar to that the ovary of the Caryophyllaceae. verifying this con-

clusion, two remarks must be made:

a. As is demonstrated above, some of the illustrations of Ihlenfeldt are inconsistent with

in examination of the observations the present study. Moreover, of some other genera

the Mesembryanthemaceae (just started) demonstrated that the vascular groundplan, to

which all Mesembryanthemaceae should be reduced, is much more complex than would been from have expected the present study. b. There is no unanimity in the interpretation of the placental vascularisation in the

Caryophyllaceae (see e.g. Bocquet, 1959; Moeliono, 1970; Rohweder, 1967, 1970;

Thomson, 1942). Therefore a critical examination of the literature and even of the

flowers of some Caryophyllaceae is necessary.

The vascular pattern in the flowerof Melandrium rubrum (Weig.) Garcke and ofMyosoton Moench. have been studied This demonstrated that aquaticum (L.) in part. study the of floral vascularisation the outer whorls of both species is the same (unpublished). At it is in floral the moment safe to say that the vascular patterns the outer whorls of Melandrium and the wall of show of ovary Aptenia a high degree similarity, despite some differences.

the 4.4. The interpretation of inferior ovary.

the basis of the vascular of inferior Traditionally, on pattern two types ovary are of the vascular distinguished (Douglas, 1957; Eames, 1961). Comparison pattern in an with in led the that inferior ovary that a superior ovary to theory an inferior ovary can be formed adnation of of floral the by the bases the outer whorls to carpels (' appendicular- that inferior be of type'), or an ovary can formed by invagination the receptacle ('recep- The latter has of stelar each tacular-cup-type'). two systems bundles, system demonstrates

in a transverse section a circle of vascular bundles, theinnerbundles are inverted. According

Puri zonal to (1951, 1952), however, an inferior ovary can originate by growth, and the ofthe wall will with the morphological nature ovary vary region which is most active in

zonal growth. He suggested that there is an intermediate condition between the 'appen- dicular-type' and the 'receptacular-cup-type', perhaps recognisable only in histogenetic and cytological studies. Leins (1972) observed in an ontogenetic study that an inferior 200 BLUMEA VOL. 23, No. I, 1976

is formed in the tissue underneath the of the ovary by intercalary growth primordia gynoecium, the androecium, and theperianth. In his opinion there is only the 'receptacular- cup-type'. of According to Ihlenfeldt(i96i) the ovary the Mesembryanthemaceae in general must be considered as a 'receptacular-cup'. Traditionally, and in the opinion of the present author, it in is should be possible to detect this the vascular pattern, as e.g. the ontogenetic shifting of the Dorotheanthus the inverted placentation in (4.1.). In present study, in Aptenia no is is of bundles are found. Moreover, as mentioned above (4.3.), there a high degree of the whorls Melandrium similarity in the vascular pattern outer floral of (with a superior of wall inferior the ovary) and the ovary of Aptenia (with an ovary). So on basis of the

is vascular pattern in the flower one tempted to think that the inferior ovary of Aptenia

in there vascular must be interpreted as an 'appendicular-type'. However, Aptenia are two commissures on the level of the hypanthium rim. From the outer one the midveins and

of the inner the lateral bundles sepals are given off, from the one many bundles are given Melandrium off to the stamens and staminodes. In such commissures cannot be observed, nor in other species of the Caryophyllaceae (Thomson, 1942). In Oenothera de Vos (1975) of in inter- observed a commissure on the level the hypanthium rim which structures, that he the of the preted as leaf-gaps, occur. On ground interpreted outer regions ovary inferior of wall as stelar, so the ovary Oenothera must be considered as a 'receptacular-cup'.

If in the commissures in Aptenia structures like leaf-gaps could be inferred, the inferior

could be this information is ovary interpreted as a 'receptacular-cup'. However, as

not to be which of inferior not yet available, it is possible certain as to type ovary is needed. present in Aptenia. A detailed examination of the commissures is Regarding

Dorotheanthus, one is tempted to think that the inferior ovary must be considered as a

because of the ofinverted vascular bundles. these 'receptacular-cup', presence However, the ventral bundles inverted the result of the in the are carpellary (D), as shifting ovary wall. In an ovary of the 'receptacular-cup-type' the inverted bundles are stelar ones

(Douglas, 1957; Eames, 1961). Moreover, the vascular pattern in Dorotheanthus can be

in Because it is interpreted as being derived from that Aptenia (4.1.). not yet clear which of inferior the Dorotheanthus. type ovary is represented in Aptenia, same applies to

4.5. Conclusions. the vascular the flowers of and Dorotheanthus In comparing patterns in Aptenia cordifolia

bellidiformis it is concluded that the vascular pattern of the pseudo-parietal placentation in be derived from that Dorotheanthus must interpreted as ofthe axile placentation in Aptenia by a shifting in the ovary wall. So typologically Dorotheanthus must be considered as

it derived from Aptenia. As a result of the foregoing can be stated that:

1. The vascular bundles in the flower shQW relative conservatism within the groundplan.

For example, the ventral carpellary bundle D has not shifted from its position in the

radius with the of the fact this would septal to a position alternating septa inspite give shorter distance both from the of the end of the it a to travel, point origin to bundle,

and from this bundle to the whole placenta. However, the branches E from bundle D

to the placenta are much more extensive in Dorotheanthus than they are in Aptenia. General remarks 2. concerning Aptenia apply also to Dorotheanthus. More research needs

to be done into the vascular pattern in Aptenia and into the comparison between the

vascular in the floral whorls of Melandrium and the wall of pattern outer ovary Aptenia

before it is possible to be sure wether the 'appendicular-' or 'receptacular-cup-type'

of ovary is present in Aptenia and in Dorotheanthus which is derived from Aptenia. C. van der Meulen-Bruijns: The flower of some Mesembryanthemaceae 201

ACKNOWLEDGEMENTS

I wish sincere thanks Dr. B. M. Moeliono for the and and for to express my to encouragement discussions, his in the ofthis Thanks also due to Mrs. A. who introduced helpful guidance preparation paper. are Dijkstra into the several I Mrs. Y. M. Butler for the me techniques.Finally, am grateful to correcting English text.

5. REFERENCES

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