Systematic Wood Anatomy and Affinities of The

wood and affinities of the Systematic anatomy Urticaceae

K.J. Bonsen and B.J.H. ter Welle

With 19 figures and 7 tables in the text

Abstract

& H.: Bonsen, K.J. ter Welle, B.J. Systematic wood anatomy and affinities of the

Urticaceae. — Bot. Jahrb. Syst. 105: 49—71. 1984. — ISSN 0006-8152.

The wood of all of anatomy tribes the Urticaceae, a family of herbs, shrublets, and sometimes shrubs, trees or lianas, has been studied and described in detail. Special atten- tion is the of the characters in of given to interpretation terms taxonomy and phylo-

A in is geny. classification, part deviating from the existing morphological classification, presented. Finally, the relationship within the Urticaceae, as well as the relationships with the Ulmaceae and Moraceae (including Cecropiaceae) are discussed.

1. Introduction

There doubt is no about the close relationships between the taxa of the Urticales. The main systematic problem is the subdivision of the order into taxa of lower rank. Some taxonomists (BENTHAM & HOOKER 1880) recognize only one family within this order, whereas others (ENGLER 1889, CRONQUIST

1981) prefer the concept of 3 to 5 families (Table 1).

The Cannabaceae have been studied the two of this not as genera family herbaceous. The Ulmaceae be from the other are always can easily separated

families by flower and fruit characteristics.

characters less obvious for the of Mo- Discriminating are group consisting Urticaceae. Taxonomic have raceae, Cecropiaceae, and studies of the Moraceae

carried been out most recently by Dr. C. C. Berg, Institute of Systematic Bot-

while anatomical studies conducted in the Institute any, Utrecht, are same by

0006-8152/84/0105-0049$ 06.00

4 Botanische Jahrbiicher, Bd. 105 50 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Table 1. Classificationof the Urticales.

Bentham & Hooker Engler Cronquist

1880 1889 1981

ULMACEAE

Ulmeae Ulmoideae

Celtideae Celtoideae ULMACEAE

MORACEAE

Cannabineae Cannaboideae CANNABACEAE

Moreae Moroideae MORACEAE Artocarpeae Artocarpoideae Conocephaleae Conocephaloideae CECROPIACEAE

Urticeae URTICACEAE URTICACEAE

Koek-Noorman, Topper and ter Welle (in press). Berg (1978) separated

the the this Cecropiaceae (6 genera) from Moraceae. A detailed study of new carried family was out by Bonsen & ter Welle (1983). The results obtained

from this the exclusion of the from the study justify genus Poikilospermum The with of the Cecropiaceae. similarity some species Urticaceae supports its inclusion this of in family, although the proper place Poikilospermum within the Urticaceae remained doubtful.

The with the of this present paper deals, among others, systematic position the genus in Urticaceae. At the same time it completes the wood anatomical

of the The wood survey Moraceae/Cecropiaceae/Urticaceae complex. anatomy the Ulmaceae of has not been studied. As this family stands beyond dispute

within the Urticales, wood anatomical data from the literature will be used to

discuss the relationship of Ulmaceae with the other families.

The Urticaceae constitute a of about and family 50 genera 2000 species

(Hutchinson 1967), mainly consisting af annual or perennial herbs and shrub-

Table 2. Classification of the Urticaceae (Engler 1889). for this (The woody genera investigated study.)

UREREAE BOEHMERIEAE

Dendrocnide Boehmeria Phenax

Gyrotaenia Debregeasia Pipturus Laportea Leucosyke Poikilospermum

UreraUrera Maoutia Pouzolzia

Urtica Myriocarpa Touchardia Neraudia VillebruneaVillehrunea

PROCRIDEAE PARIETARIEAEPARIETARIEAE FORSSKAOLEEAE

Pilea Gesnouinia Forsskaolea

Procris K. J. Bonsen & B. J. H. ter Welle, Urticaceae 51

lets, sometimes shrubs, trees, or lianas. The geographical distribution is given by Engler (1889): 33% New World, 33% Asia and Malesian Archipelago,

14% Africa, 14% Oceanic Islands, and 3—4% Europe. A classification of the

Urticaceae Bentham& Hooker and Engler was given by (1880), (1889), see also Table 2.

In his of monographic treatments the genera Poikilospermum (1963), Lapor- tea (1969b), and Dendrocnide (1969c) Chew Wee-Lek transferred the woody species of to Dendrocnide. The Neraudia revised Co- Laportea genus was by

wan Chew Wee-Lek described Nothocnide (1949). Finally, a new genus for-

included in merly Pipturus (1969a). Anatomical studies of the Urticaceae were made by Bigalke and SOLEREDER (1933) (1899, 1908). A comprehensive survey of the literature was published by Metcalfe& Chalk (1950).

2. Methods

macerations Sections and were prepared according to standard techniques, and em- bedded in Canadabalsam and in glycerin respectively. used is that The wood anatomical terminology proposed by the Committee on No- menclature of the I.A.W.A. (1964).

wood data The quantitative were measured as follows: vessel diameters were meas-

ured in based 25 The vessel fre- tangential directions; averages are on measurements.

is based on 25 countsof of 1 In the lowest and quency areas sq. mm. descriptions high-

and the minimum and values found in est averages per specimen are given, maximum

the material studied are for both characters. The of vessels given percentage solitary was

calculated after least 100 Clusters and counting at pores. multiples were regarded as 2, 3,

4, on the number of vessels For the intervascular etc. vessels, depending per group. pits the sizes minimum and maximum are given. Vessel member length and fibre length are based on 25 minimum and maximum sizes measurements per sample. Averages, are presented. For the maximum wall thickness and lumen fibres, maximum diameters are given.

Multiseriate in in in ray height is presented micrometers, ray width micrometers and

number of cells. Both data are related the of the 25 observed to average highest rays as

in section. The numberof of 25 one rays per mm is the average counts.

3. Materials

is This study based on 85 wood specimens representing 21 genera and 50 species.

Informationon collectors number and wood collection accession numbers (abbreviations of according to Stern 1978), locality and diameter the samples is provided in Table 3.

4. Results

4.1. Description of the family Urticaceae Juss.

Growth round — rings faint or absent. Vessels diffuse, to oval; solitary (20 and in radial 95 %) multiples and irregular clusters of 2—4 (20); 2—30 (1 —100) 52 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Table 3. Material studied.

Genus/species Xylarium Collector Locality Habit ®0

6 Boehmeria caudata Sw. ex FHOw 9954 unknownunknown T 6

Uw 20833 Lindeman 9202 Brazil T 33

Uw 23594 Maas et al. 3071 Ecuador T 33

Uw 27644 U.P.D. 776 Argentina T 10 Sw. al. Ecuador B. vs. cylindricacylindrica (L.) Uw 23595 Maas et 3072 T 3 excelsa B.B. excelsa (Bertero ex Uw 1501115011 Meyer 95979397 Juan Fern. T 88 Steudel) Wedd.

B. niveanivea (L.) Gaudich. Sandwijck s.n. Neth. Cult. T 1 B. pavonii Wedd. Uw 21090 Schunke4977Schunke 4977 Peru T 10 B. platyphylla-virgata Wedd. Uw 27817 Grant 4024 Society Isl. T 3 B. ramiflora Jacq. Uw 1544615446 Chambers 2686 Dominica T 4

B. — B. Uw 23616 426 T — spec. Berg etet al. Ecuador

Debregeasia longifolia Wedd. Uw 27818 Koorders 8841 B Indon.Indon. Java T 1.51.5

Uw 27819 Koorders 8844 B Indon. Java T 1.51.5 Uw 27820 Koorders 8843 B Indon. Java T 22

Uw 27821 Koorders 1476814768 B Indon. Java T 3 Uw 27822 Koorders 26746 B Indon. Java T 4

Dendrocnideexcelsa (Wedd.) Uw 27647 U.P.M.21IU.P.M. 211 Australia T 55 Chew

D. FHOw T — luzonensis (Wedd.) Chew ex FHOw 5283 unknown T D. microstigma (Gaudich, Uw 27828 Koorders 40042 B Indon. Java T 6 Chew exex Wedd.) Chew

D. moroides (Wedd.) Chew Uw 27829 BW 7097 Indon. Irian T 6

Uw 27830 BW7319 Indon. Irian T 4

D. rechingeri (H. Winkler) Uw 27823 Craven & Schodde Solomon Isl. T 55

Chew 515313

D. stimulans (L.f.) Chew Uw 27831 Zw.Zw. et R. 134 Indon. T —

Uw 27832 ex WIBw 22863 unknownunknown — 88

D. Uw 27824 T spec. 27824 v. Beusekom 4196 Thailand T 6

Forsskaolea angustifolia Uw 27825 Haman 130383 Canary Isl. SS 0.6

Retz

Gesnouinia arboreaarhorea (L.f.) Hortus Bot. Neth. Cult. S.S. 55

Gaudich. 76—577

Uw 2782627826 Haman 170383 Canary Isl. S. 1.51.5

Gyrotaenia microcarpa Uw 8357 ex USw 6019 Jamaica T 5 Fawcett & Rendle

candidissima Uw 27833 WIBw — — Leucosyke candidissima Uw ex WIBw 22532 unknownunknown Wedd.

L.L. capitellata Wedd. Uw 27834 Koorders 93389338 B Indon. Java T 8

Uw 27836 Koorders 14774 B Indon. Java T 10

Uw 2783527835 Koorders 11132 B Indon. Java T 8

cf. Maoutia cf. ambigua Wedd. Uw 27837 v.v. Royen 3289 Indon. Irian S 5 M. diversifolia Wedd. Uw 27838 Koorders 9323 B Indon. Java S 3

Myriocarpa stipitata Benth. Uw 21084 Schunke 4008 Peru T 10 K. J. Bonsen & B. J. H. ter Welle, Urticaceae 53

Table 3 cont.

Genus/species Xylarium Collector Locality Habit 0®

Nee 7146 PanamaPanama S 4 M. yzabalensis (J. D. Smith) Uw 29521 Killip Maas al. 2911 Ecuador T 5 M. Uw 23574 et spec. Ecuador T 9 Uw 23614 Berg 420

Neraudia kauaiensis Uw 27841 Degener Hawaii Isl.Isl. S 0.5

(Hillebr.) R. Cowan 1511—174591511—17459

N. N. melastomaefolia Uw 2784327843 St. John 080233 Hawaii Isl. S 1 Gaudich.

Uw 2784427844 Carlquist 1958 Hawaii Isl.1st. S 2

Uw 27845 ForhesForbes 5/23/20 Hawaii Isl. S.S. 0.5

Nothocnide discolor Elmer 13859 Philippines C — (C.(C. Robinson) Chew

N. repandarepanda (Blume) Blume Uw 27857 de Vogel 4410 Indon.Mol. C 11

Uw 27858 Koorders 20736B Indon. Java C 4 N. Uw spec.spec. 27860 Jacobs 91339133 Papua N.G. C 2

J PhenaxI henax angustifoliusangustifohus Kunth Uw 27846 Schunke 3973 Peru S 1.5 Wedd.

Pilea Uw 23592 Maas al. 3059 H 1.2 spec.spec, et al. Ecuador

Uw Pipturus albidusalhidus Uw 27645 U.P.M.318U.P.M. 318 Hawaii Id.Isl. T 4 A. A. Gray ex Mann

P. argenteus Uw 27848 Grant 4561 Society Isl. T 2

(G. Forster) Wedd. SFCw R977 unknownunknown — 10

—239

P. incanus Wedd. Koorders Uw 27851 Koorders 9573 B Indon. Java T 10

Uw 27855 ex WIBw 13354 Indon. T 2

P. Indon. spec. Uw 27859 Hoogland 3382 Indon. IrianIrian T 3

Poikilospermum amboinenseamhoinense Uw 26781 Lam 647 Indon. Irian C 2

Zipp. ex. Miq.

P. Chew Uw inaequale Chew Uw 26780 Docters v. Leeuwen Indon. C 1

9671

P. naucleiflorum (Roxb.(Roxb. Uw 27519 RTIw 1507 unknown Cc 3 apud Lindley) Chew

P. suaveolens (Blume)(Blume) Merr. Uw 27020 JacobsJacobs B 502502 unknown Cc 4 Uw 27516 de Vogel 4516 Indon. Mol. Cc 2

Uw 27518 Koorders 35779 B Indon. Java Cc 2

P.P. Uw 27517 9575 N.G. C spec.spec. JacobsJacobs 9575 Papua N.G. c 2 Pouzolzia siminea Wedd. Uw 27861 Koorders 26609 B Indon. Java Ss 11 Procris frutescens Blume Uw 27862 Pleyte 522 Indon. Irian Ss 11 P. reticulato-venosareticulato-venosa Uw 27864 Biinnemeyer 1172 Indon. Sum. L 11 (Hall)(Hall) Schroeter

P. Uw 27866 8469 Indon. Sum. L 11 spec.spec. JacobsJacobs Touchardia latifolia Uw 18601 SternStem & Herbs1518Herbst 518 Hawaii Isl.Isl. S 5 Gaudich.

UreraUrera baccifera (L.) Uw 29522 Nee 7148 PanamaPanama S 3 Gaudich.

U. cameroonensis U. cameroonensis Wedd. Uw 9332 Breteler 1500 Cameroun L 6

Uw 9443 Breteler 2037 Cameroun L 4 54 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Table 3 cont.

Genus/species Xylarium Collector Locality Habit ®

U. caracasana Griseb. Colombia L caracasana(Jacq.) Uw 25080 Cuatrecasas 14509 L 4 Uw 2765027650 U.P.D.784U.P.D. 784 Argentina L 3 U. elatadata (Sw.) Griseb. Uw 27194 Mathias & Taylor Peru S 1

53435343

U. hypselodendron Wedd,Wedd. Uw 15936 Schlieben 1721 East Africa L 33

Uw 27404 s.n. Zimbabwe L 5 Uw 27404 Berg s.n. L 5

Uw 27646 Schlieben 4683 East Africa LL 3

U. laciniataWedd. Uw 3902 Lindeman 5660 Surinam T 44

U. cf. myriocarpa Uw 8662 Ellenberg 22752275 Peru T 3 robustarohusta Chev. U. A. Uw 27868 Versteeg en Ivory Coast T 11

den Outer 178178

Urtica L. H 1 Urtica dioica Uw 27869 ter Welle s.n. France 1

BonsenBonsen s.n. Nethl. H 0.5

Niloufari IranIran H 1 U. monfohamorifolia Poiret Uw 27871 Human 160383 Canary Isl.Isl. H 0.5 Villebrunea rubescensruhescens Blume Uw 27880 de Vogel 2545 Indon.Indon. Cel. T 7

V. Uw 27882 Craven & Schodde N.G. T 6 Kspec.spec. Papua

983

Uw 27643 SeihtSeibt 38 Indon.Indon. Java T 88

= Legenda: Habit: T = tree or treelet; S = shrub; C = climber; L = liana; H herb; ®:

diameterof the wood sample in cm.

diameter vessel member per sq. mm; 40—360 (25—480) pm; length 195—525 Perforations (130—1230) pm. simple. Intervascular pits alternate, round or po-

6—18 sometimes scalariform. Thin-walled or ab- lygonal, pm, tyloses present

sent.

in radial and Fibres 370—1745 (170 —2139) pm long; with simple pits the all storied in lu- tangential walls; non-septate or partly septate, some genera;

diameter 9—30 walls 2—7 fibre sometimes men pm; pm thick; dimorphism

short fibres and present: very long fibres, length 3400—5000 pm.

Uniseriate absent if of and rays mostly or scarce, present composed square

cells. Multiseriate 2—6 sheath cells upright rays (0—8) per mm; mostly pres-

ent almost of and ; heterogeneous, entirely or entirely composed square upright several of and cells, to mm with central cells up high or a part procumbent

of — marginal rows square or upright cells, 600—1940 (420 —2850) pm high; 3

10 cells = 45—255 sometimes (15) (40—390) pm wide; containing druses,

rhombic vitreous silica. of the with crystals, or In part genera unlignified par- the enchyma (see below) rays are sometimes partly unlignified too. of If Vasicentric paratracheal parenchyma in strands 2—4 (8) cells. apotracheal is it is islands bands parenchyma present, unlignified, occurring as or as in sometimes vitre- seen cross-section; containing druses, raphides, styloids or

ous silica.

Specific gravity: 0.25—0.70. K. J. Bonsen & B. J. H. ter Welle, Urticaceae 55

4.2. Descriptions of taxa of the Urticaceae

For this 21 studied. be study genera were They can separated already at first view into two based the absence of groups, on presence or unlignified elements. Within these A and the groups B, overlap in wood anatomical char- is considerable. acters Therefore a of these two is description groups presented, instead of 21 separate generic descriptions.

Group A. Boehmeria, Debregeasia, Forsskaolea, Gesnouinia, Leucosyke, Maoutia,

Neraudia, Phenax, Pipturus, Pouzolzia and Villebrunea(Fig. 4 and 5).

faint Growth absent. — rings or Vessels diffuse, round to oval; solitary (35 and in 85%) radial multiples and irregular clusters of 2—4 (6); 3—30 (1—45) 70—180 in member per sq. mm; (55 —230) pm diameter; vessel length 240— 525 Perforations Intervascular (155—1230) pm. simple. pits alternate, round or

6—12 Thin-walled absent. polygonal, pm. tyloses present or

Fibres 665—1745 with (360 —2130) pm long; simple pits in the radial and

tangential walls; in Boehmeria and Villebrunea septate p.p., Pipturus p.p. p.p.; in the other lumen diameter walls non-septate taxa; 15—30 pm; 2—7 pm thick.

Uniseriate rays occur in Leucosyke and Maoutia and occasionally in Piptu- Boehmeria, and Villebrunea, and rus, are composed of square and upright cells.

Multiseriate 3—6 sheath cells al- rays (7) per mm; usually present; entirely or

most of and several entirely composed square upright cells, up to mm high;

3—8 cells = (11) 50—150 (45 —180) pm wide; containing druses in Boehmeria

and Villebrunea rhombic p.p., Pipturus p.p., p.p.; crystals in Pipturus p.p. and Villebrunea vitreous silica p.p.; in Leucosyke p.p.

Parenchyma scarce, paratracheal, vasicentric, in strands of 2—4 (8) cells.

Specific gravity: 0.30—0.70.

Note The herbs and small shrublets this : belonging to group A (Forss- kaolea, Gesnouinia, Neraudia kauaiensis) differ from the description given before in the following characters: Vessels solitary (45—95%), in N. kauaiensis

20 %; 20—70 diameter 45—70 vessel member per sq. mm; (25 —95) pm; length 195—275 Intervascular (130—370) pm. pits 6—12 pm, sometimes scalariform. Fibres 425—575 lumen diameter walls 2—4 (265 —755) pm long; 12—15 pm;

thick. 2—7 cells = pm Rays (8) per mm; 3—5 (8) 45—60 (40—85) pm wide; containing druses in Forsskaolea.

Group B. Dendrocnide, Gyrotaenia, Myriocarpa, Nothocnide, Pilea, Poikilo-

spermum, Procris, Touchardia, Urera, and Urtica (Figs. 6, 7 and 11).

Growth faint absent. Vessels round — rings or diffuse, to oval; solitary (45 85%) and in radial and multiples irregular clusters of 2—4 (6); 2—15 (1—25) diameter per sq. mm; 100 —270 (120—310) pm; vessel member length 295— 460 (205 —540) pm. Perforations simple. Intervascular pits alternate, round and

polygonal, 8—15 Thin-walled pm. tyloses present or absent. 56 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Fibres 825—1255 with in the radial and (370 —1650) pm long; simple pits

tangential walls; non-septate and occasionally septate in Gyrotaenia-, lumen diameter walls Storied fibres in and 12—24 pm; 3—6 pm. Dendrocnide, some-

in other and times, but less strikingly so the genera, except Gyrotaenia Myrio-

carpa.

Uniseriate absent. Multiseriate 1—4 sheath cells rays rays (0 —6) per mm; almost of mostly present; heterogeneous, entirely or entirely composed square and upright cells, up to several mm high or with a central part of procumbent

cells and of and 600—1940 marginal rows square upright cells, (420—2850) pm

cells = high; 3—10 (15) 50—255 (45—390) pm wide; sometimes partly unligni-

druses in Urera in fied; containing Gyrotaenia p.p. and p.p., and cystoliths Gy-

rotaenia p.p.

of cells. Paratracheal parenchyma as vasicentric rings, in strands 2 —4 (5)

in Apotracheal parenchyma unlignified, occurring as islands or bands cross-sec- and tions; containing druses in Gyrotaenia, Myriocarpa Urera ; containing ra-

all but one of Dendrocnide in Dendrocnide phides in specimen ; styloids p.p.,

and vitreous silica in Dendrocnidemoroides.

Specific gravity: 0.25—0.55.

Notes: The herbs and small shrublets to this B ( Urtica belonging group , Procris, and Pilea) differ from the description given before in the following

characters: — Vessels diameter 40—85 25—100 per sq. mm; (25—110) pm; vessel member length 205—250 (155 —310) pm. Intervascular pits 6—9 pm,

sometimes scalariform. Fibres 370—435 (170 —590) pm long; non-septate;

lumen diameter walls thick; sometimes storied in 9—15 pm; 3—5 pm slightly

Procris and Urtica. — Rays composed of fusiform parenchyma cells in Procris

and Urtica with cells in and in Procris ; high rays upright Pilea, unlignified rays reticulata-venosa.

this B The climbers and scramblers of group (Nothocnide, Poikilospermum.

Urera p.p.) differ from the description given before in the following characters: radial Vessels solitary (45—80%) and in multiples of 2—4 (20); 5—9 (2—15)

diameter vessel member length 270— per sq. mm; 260—360 (180 —480) pm; Fibre in 480 (225 —590) pm. Intervascular pits 9—18 pm. dimorphism present

Poikilospermum and Nothocnide; short fibres with a lumen diameter of 18—26

walls and sometimes pm, 2—6 pm thick, 545—865 (370 —1175) pm long, slight- the other Nothocnide the short fibres ly storied; type over 3000 pm long. In

and sometimes — unligni- are very scarce unlignified. Rays mainly or totally fied. Apotracheal parenchyma unlignified, containing druses in Poikilospermum, often addition. Nothocnide, and Urera, rhombic crystals present in

differences and variations in the Although some generic occur Urticaceae, well-defined the wood anatomical fea- the family constitute a group as regards

There exclude of the studied here from tures. are no arguments to one genera the family. K. J. Bonsen & B. J. H. ter Welle, Urticaceae 57

5. Discussion

5.1. Discussion of and value of diagnostic, taxonomic, phylogenetic some wood anatomical features

Unlignified elements

The all of unlignified elements, characterizing taxa group B, are sometimes absent faint in the of in or early stages secondary growth the erect or climbing shrubs and trees. The herbaceous species show unlignified bands from the be-

of their With the number ginning secondary growth (Fig. 7). increasing girth as well the as proportion (as percentage of the transverse section) of these unlignified elements increases. The of the elements formed majority is by axial paren- is islands chyma and shown as or bands (Fig. 6). The most extreme state of this character is found in Dendrocnide where continuous bands occur.

the of the the also In secondary xylem climbing species rays are unlignified, of surrounded resulting in a typical pattern of isolated islands vessels by ligni-

in the fibres fied elements (Fig. 8 and 9). Sometimes, e.g. Nothocnide, part of and also rays remain unlignified (Fig. 11).

existence The of this feature might well be explained in terms of mechanical strength: it occurs in lianas, climbers, and in the tall erect herbs with stems

small like the other hard having a diameter, e.g. Urtica (Fig. 7). On hand, it is how the to see above could apply to plants of tree-like habit.

Fibre dimorphism

of the Species climbing genera Poikilospermum and Nothocnide show fibre The main difference between the fibre dimorphism. two types in Poikilosper- and Nothocnide is the fibre mum length. Apart from normal fibres (see here- fibres section after), very long (over 3000 pm) are also found. In transverse distributed islands. these long fibres are as (small) The short fibres in these

those found in is shown genera are comparable to elsewher the Urticaceae, as in the following comparison:

fibre in length Poikilospermum/Nothocnide 545— 865 pm;

fibre in other taxa of length group B 825—1255pm;

fibre length in taxa of A 665—1745 group pm. Even when of the remain the most short fibres unlignified, long fibres are

these lignified (Fig. 8). The occurrence of long fibres might be related to the

climbing habit of Poikilospermum/Nothocnide. This idea is strengthened by the 58 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

results of investigations by A. M. W. Mennega (pers. comm.), who compared of families. the wood anatomy climbing and non-climbing taxa in various In

lianas have than like in the general, longer fibres tree species same family.

Crystals

of are Some the genera possess crystals in the axial parenchyma. Druses

sometimes in rhombic most common, although they occur combination with

Intermediate neither be crystals. crystal forms which can properly described as

rhombic sometimes in the a druse, nor as a type, occur same parenchyma strands. the rhombic is limit- As a result, presence of druses and/or crystals of ed taxonomic value. absence of is However, or presence raphides very impor-

found all of tant in terms of taxonomy, as raphides are in samples except one

of the Dendrocnide, and have not been observed in any other sample Urtica-

ceae studied.

Rays

The of the Urticaceae show features in their rays juvenilistic composition: and cells great height predominantly erect (CARLQUIST 1962). Some genera, where Dendrocnide in the mature e.g. (Fig. 13) possess rays secondary xylem the is in the first juvenilistic stage not immediately recognized. However,

formed of these is vis- secondary xylem taxa juvenilistic ray composition clearly ible (Fig. 12). of of be- The rays the representatives group A can easily be interpreted as

derived from of and ing a juvenile stage Kribs’s (1935) heterogeneous types I II found and (Fig. 16). Uniseriate rays are always in Maoutia Leucosyke, they are

sometimes present in Pipturus, Villebrunea and Boehmeria. No uniseriate rays

were observed in Neraudia Pouzolzia, Gesnouinia Forsskaolea, Debregeasia, , , and Phenax.

of the much wider of In In group B Urticaceae a range ray types occurs. first the the formed secondary xylem two basic ray types can be distinguished:

and wide and the and The wide high rays (Fig. 12) high narrow rays (Fig. 15). the rays can be considered as medullary rays (Fig. 10). In mature secondary

these tend become less dissected and xylem rays to wider; or they are probably of cells, Dendroc- are composed more radially elongated (procumbent) ray e.g. nide (Fig. 13), Poikilospermum, and Nothocnide. with restricted i.e. the of small shrubs In taxa a secondary growth, group

and the either herbs, rays are medullary rays (Pilea; Fig. 14) or they are mainly

composed of fusiform cells (Urtica, Procris; Fig. 19). In the shrubby genus Touchardia the tissue which is medullary rays are replaced by parenchymatic

hardly distinct from the fibre tissue (Fig. 18). K. J. Bonsen & B. J. H. ter Welle, Urticaceae 59

The and found in with almost narrow very high rays are species an com-

closed of elements. the pletely cylinder primary xylem In mature secondary xylem of and the become dissected and Myriocarpa Gyrotaenia rays sometimes become wider. the cells Simultaneously, ray are more radially enlarged or procumbent.

The of dissected does in the phenomenon rays not occur climbing species of Urera, Poikilospermum, and Nothocnide. As stated before, with increasing

diameter and cells become these stem more more ray unlignified in taxa (Fig. 8 and 9).

5.2. Subdivision of the Urticaceae and the position of Poikilospermum

The woody Urticaceae, including Poikilospermum (Bonsen & ter Welle be can into two well the wood 1983) separated dinstinguishable groups using be the absence anatomical characters (Table 4). They can recognized easily by of elements or presence unlignified (commonly axial parenchyma).

Table 4. Relevant wood anatomical characters of the shrubs and of A and trees group B of the Urticaceae (see § 4.2).

Group A Group B

Vessels per sq. mm 3—30 2—15

Vessel diameter(pm) 70—180 100—270

Uniseriate rays present or absent absent of multiseriate cells and often Shape ray upright/square upright/square procumbent (herbs with fusiform parenchyma) Numberof multiseriate rays/mm 3—6 1—4

Apotracheal parenchyma absent present, unlignified

A contains the tribes Forsskaoleeae and Parietarieae. the Group In group B

tribes and Procrideae are found. Urereae Most genera of the tribe Boehmerieae

belong to group A (see Table 5), but Myriocarpa, Touchardia, and Nothocnide

show all features The classification of the defining group B. family in tribes, based mainly on flower characteristics WEDDELL was (see, e.g. 1856), already

disputed by BlGALKE (1933) on the base of leaf anatomical features. For in-

the of stance presence elongated cystoliths and the absence of hooked hairs in

and Touchardia Myriocarpa (Nothocnide was not investigated) points towards a the Urereae and Procrideae. be said that position near In conclusion, it may

both wood and leaf thus indicate that the Boehmerieae anatomy anatomy are a

and should be re-evaluated. heterogeneous group,

Poikilospermum (BlGALKE 1933) is said to have elongated cystoliths, while

hooked hairs are not reported. BlGALKE’s suggestion of similarity of Poikilo-

with Urereae and accordance with spermum Procrideae, again, is in our find-

ings, which place B, rather than in A. In Poikilospermum near group group 60 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

the wood is from fact, genus Poikilospermum, anatomically, not distinguishable

the and similar of genus Nothocnide, is very to the climbing species Urera (see also Table 6).

5. A Table Relevant wood anatomical characters of individual genera of group of the

Urticaceae (see § 4.2).

Trees/treelets/shrubs Herbs

Leu. Mao. Boe. Pip. Vil. Pou. Deb. Ner. Phe For. Ges.

+ Uniseriate rays + (+) (+) {+)--- f+)

Septate fibres — — (+) (+) (+)____ — —

Druses — — (+) (+) (+)---- (+) -

Rhombic crystals — — — (+) (+)----

+ = in = in of — = Legenda: present all specimens; (+) present part the specimens; the absent. Only the first three letters of genera are mentioned.

Table 6. Relevant wood anatomical characters of individual of the genera group B of Urticaceae (see § 4.2).

Trees/treelets/shrubs Climbers Herbs

Gyr. Myr. Tou. Ure. Den. Not Poi. Ure. Urt. Pro. Pil.

Septate fibres f+)

Druses + + — + — + + + (+) + +

Raphides — — — — + — — — — —

Rhombic crystals — — — — — (+) (+) (+) — — —

Stoned fibres — — (+) (+) + (+) (+) (+) (+) (+) (+)

Legenda: see Table 5.

5.3. Phylogeny in the Urticaceae

within the wood To clarify the phylogenetic relationships Urticaceae some of anatomical characters can be used. Relevant characters in terms phylogeny

and of the are: ray type composition, fibres, presence unlignified elements, oc-

of storied fibres and currence raphides.

Ray composition

Trends for the of have been established Barghoorn specialization rays by

uniseriate and the (1941b). He recognized two trends: the elimination of rays, K. J. Bonsen & B. J. H. ter Welle, Urticaceae 61

elimination of multiseriate In both trends the of the rays. composition rays from and into cells. changes square upright procumbent ray

The of A of the Urticaceae similar to the representatives group possess rays of the trends estab- heterogeneous ray type Kribs (1935). Taking into account lished by BARGHOORN these have to be considered as a (1941b), rays juvenile form of these heterogeneous rays. This juvenile type is most prominent in

Maoutia and where both uni- and multiseriate The Leucosyke, rays are present. in and Boehmeria show reduction of ray patterns found Villebrunea, Pipturus, a the uniseriate in Pouzolzia and Neraudia uniseriate rays. Finally, , Debregeasia,

are lost further reduction of cambial rays completely (see also Fig. 1). A

results in of the multiseriate like in activity diminishing proportions rays, e.g. Phenax.

The variation observed in the of the of B is as ray composition taxa group much wider and be in the trends cannot explained terms of phylogeny using established by BARGHOORN (1941b). However, the ontogenetic variation in the

the various remark- material studied, and the differences between species, agree

with the ably well theory on paedomorphosis as presented by Carlquist

Some of the taxa of B which can be considered as (1962). group possess rays descendent from wide and which are linked medullary rays: very high rays, with the In the of the pith. ontogeny secondary xylem new rays are not formed. of isolated This pattern wide medullary rays and completely secondary

is in xylem parts common herbs.

other of The taxa B but These group possess very high, narrow rays. rays linked with the but are pith, are bound by primary xylem elements situated close to each other or almost forming a closed ring. These taxa have a stem which is herbaceous Plants hardly anymore. with an irregular, almost closed ring of primary produce both wide and These xylem narrow rays (Fig. 17). nar- still have the row same as the This towards rays height medullary rays. points a

herbaceous ancestor.

A correlation between both phylogenetic trends in the Urticaceae remains

cambial mentioned before for hypothetical. Decreasing activity, group A, in would result a herbaceous like and ulti- subshrubby or habit, e.g. Phenax, in herbs. division the leads isolated mately Here, the of primary xylem ring to vascular bundles, separated by medullary rays. The secondary xylem produced these in herbs does not from but possess rays originating primary xylem, only linked with the like rays directly medullary rays, in e.g. Urtica and Pilea.

On the other hand, an increasing cambial activity would result in shrubs and Dendrocnide, and sometimes climbers like in trees, e.g. e.g. Poikilospermum and Nothocnide. In these last two taxa still Gradual medullary rays are present.

closure of the cylinder results in with in the primary plants narrower rays sec- like in and schematic ondary yxlem, e.g. Gyrotaenia, Myriocarpa, Urera. A

of the lines of of the in the Urticaceae is survey possible specialization rays presented in Fig. 1. 62 K. J. Bonsen & B. J. H. ter Welle,Urticaceae

processes. underlying

the and Urticaceae

the

in development

ray

of sequence Possible

1. Fig. K. J. Bonsen & B. J. H. ter Welle, Urticaceae 63

Fibres

Als mentioned in already before, fibre dimorphism occurs Poikilospermum and This is trend within Nothocnide. phenomenon regarded as a specialization

the Urticaceae. The wood of Urera is similar to that of Poikilo- anatomy very and does spermum Nothocnide. However, fibre dimorphism not occur. Storied fibres of non-storied are generally accepted as being a specialization

fibres BAILEY in (e.g. 1920, 1923, JANSSONIUS 1931). Storied fibres are scarce the and observed of Urticaceae, were only in some genera group B. They oc-

sometimes not in Procris, Urtica cur, although very clear, Pilea, Touchardia,

and the of Storied fibres are in non-climbing species Urera. very prominent Dendrocnide, Poikilospermum (all climbers), Nothocnide (all climbers), and the

climbing or lianalike Urera-species.

Unlignified elements

The of elements in the Urticaceae with occurrence unlignified regard to

function has been discussed before. As it is hard to see how these elements

could contribute mechanical in of tree-like to strength plants habit, one might

that the trees of descendants from herbaceous suggest group B are ancestors.

Habit

The of and the occurrence paedomorphosis in all Urticaceae trends of spe-

cialization of the towards with limited cambial rays point a common ancestor

a small shrub or a herb. The overall of activity (CARLQUIST 1962): presence from the indicates that the of herb. rays originating pith ancestor group B is a

This is also characterized the of elements. group by occurrence unlignified This towards herbaceous character, too, points a origin. A possible habital of pathway the group is presented in Fig. 2.

Fig. 2. Possible habitalpathway of the Moraceae and the Urticaceae. 64 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

5.4. Phylogeny in the Urticales

Apart from the suggestion to include Poikilospermum in the Urticaceae,

Bonsen & ter Welle the 5 of the (1983) proposed to assign remaining genera

Cecropiaceae sensu Berg to the Moraceae, based on the fact that neither leaf

wood anatomical the the nor features were found to distinguish taxa of two families.

will be dis- The affinities and a possible phylogeny within the Urticales cussed here, based on some wood anatomical features, commonly considered to have phylogenetic value.

The trend from general phylogenetic scalariform to simple perforation

and his plates as established by Bailey students (1920, 1923), is supplemented by CARLQUlST’s theory of paedomorphosis (1961, 1983), and Carlquist’s and

Baas’s contributions to wood therefore ecological anatomy (1973). It is, not consider the of justified to Ulmaceae as primitive within this order on the base the occurrence of scalariform perforation plates alone.

In the Urticales fibres in all Moraceae and in septate are found nearly some

Urticaceae, but in the Ulmaceae. that the never METCALFE (1983) suggests formation of of as this septa represents some kind specialization. However, character is restricted taxonomic to some groups only, it is impossible to es- tablish trend the whole. a phylogenetic for angiosperms as a TiPPO (1938) concluded from his of the fibres study Moraceae and presumed allies that septate

than fibres. are more specialized non-septate

libriform fibres found. In the Urticales, only are The simple pits mainly oc-

in the radial walls with the Urticaceae. the cur exception of the Here, simple

both radial and but pits occur in tangential walls, mostly in equal quantities, sometimes the pits in the tangential walls outnumber those in the radial walls.

We can interpret this phenomenon either as an intermediate structure between fibre-tracheids and libriform feature derived from the fibres, or as a specialized normal libriform fibre type.

mentioned storied the Urticales As already before, fibres in are only found

in the tribes Procrideae and Urereae of the Urticaceae. Based on this character

Urticaceae the must be regarded as the most specialized within the order.

trends in of Kribs Evolutionary ray types dicotyledons are given by (1935) and Barghoorn (1940, 1941a, b). Within the Urticales the most important trend from and is heterogeneous type I to heterogeneous type IIA IIB. Rays

with cells considered be increasing length of erect are to highly specialized by

considered this Barghoorn; Carlquist (1983) feature as an expression of paedomorphosis.

The Ulmaceae I and the show show heterogeneous ray types IIA, Moraceae

and the Be- heterogeneous IIA IIB. In Urticaceae juvenilistic rays are common. which show sides, a certain specialization is found in some woody taxa “is-

lands” of cells in these procumbent rays. K. J. Bonsen & B. J. H. ter Welle, Urticaceae 65

Evolutionary trends of unlignified elements are not mentioned in the litera-

Urticales Therefore ture. In the it occurs only in the Urticaceae p.p.. the pres-

of elements considered within the ence unlignified is as highly specialized Urti-

cales.

The phenomenon of fibre dimorphism has already been discussed under the

of the phylogeny Urticaceae, and is regarded as a specialization in the Urtica-

ceae.

7. Table Wood anatomical characters used to show the relationships within the Urti- cales.

Ulmaceae Moraceae Urticaceae

Perforationplates (scalariform)/ simple simple simple Fibres non-septate (septate) (septate)

Fibre location radial walls radial walls rad. & walls pit tang,

Ray type He 1/He II A (He II A)/He II B juvenile

Unligmfied elements absent absent (present) Storied fibres absent absent (present)

Raphides absent absent (present) Fibre dimorphism absent absent (present)

3. Schematical Fig. arrangement of inferred relationships in the Moraceae, Cecropiaceae, and Urticaceae based character Table on states given in 6.

5 Botanische Jahrbucher,Bd. 105 66 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Fig. 4—7. Cross-sections. — 4, Boehmeria excelsa (Meyer 9597). — 5, Gesnouinea arborea

(Haman 170383). — 6, Urera cf. myriocarpa (Ellenberg 2275). — 7, Urtica dioica (Bonsen

s.n.). Magnification for Fig. 4 —19 as indicated in Fig. 4. K. J. Bonsen & B. J. H. ter Welle, Urticaceae 67

Fig. 8—11. Cross-sections. — 8, Nothocnide repanda (de Vogel 4410). — 9, Urera came-

roonensis — Pilea al. — Dendrocnide excelsa (Breteler 2037). 10, spec. (Maas et 3059). 11,

(U.P.M. 211). 68 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

Fig. 12—15. Tangential sections. — 12 and 13, Dendrocnide stimulans (Zw. et R. 134).

— — O. 14, Pilea spec. (Maas et al. 3059). 15, Urera robusta (V. et 178). 69 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

16—19. Fig. Tangential sections. — 16, Leucosyke capitellata (Koorders 11152 B). — 17,

Poikilospermum inaequale (Uw 26780). — 18, Touchardia latifolia (Stern et Herbst 518).

— dioica 19, Urtica (ter Welle s.n.). 70 K. J. Bonsen & B. J. H. ter Welle, Urticaceae

wood Taking into account the individual interpretation of the relevant ana-

also Table be concluded that the are tomical characters (see 7), it can Ulmaceae in the most primitive family, and the Urticaceae are the most specialized family

this order. (The position of the Cannabaceae has not been studied).

schematic of the is in A arrangement phylogenetic relationships presented Fig. 3.

Acknowledgements

P. Baas Thanks are due to the following curators of wood collections: Dr. (Rijks-

herbarium, Leiden); Mr. R. Dechamps (Museum voor Centraal Afrika, Tervuren); Dr. R.B. Miller (U.S. Forest Products Laboratory, Madison); Dr. H.G. Richter (Bundes- forschungsanstalt, Hamburg), and Mr. S.I.Wisselius (Royal Tropical Institute, Am-

sterdam). Dr. J. Koek-Noorman and Dr. P. Baas are acknowledged for their comments

various of illustrations and suggestions on parts the manuscript. The were prepared by

Mr. H. Elsendoorn, Mr. H. Rypkema, and Mr. T. Schipper, the reliable artists of our

Institute. Finally, we wish to thank Drs. L. Y. Th. Westra for the most unpleasant

work: correcting the English text.

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Accepted for publication May 11, 1984

Address of the authors:

K.J. Bonsen & B. J. H. ter Welle, Institute of Systematic Botany, University of Utrecht, Heidelberglaan 2, NL-3508 TC Utrecht, The Netherlands.