202 IAWA Bulletin n.s., Vol. 8 (3),1987

MORPHOLOGY OF THE VESSEL ELEMENTS IN THE SECONDARY XYLEM OF THE FROM BRAZILIAN AMAZONIA

by

Pedro L. B. Lisboa*, J. Cesar A. da Silva*, A. A. Loureiro**, and Gracielza M. dos A. dos Santos *

Summary A morphological study of vessel elements foration plates in some genera, thus making his was carried out in species representing the five key somewhat confusing. genera of Myristicaceae present in the Brazilian In this study, we examined a large quantity Amazon region. The results show that perfora­ of wood specimens obtained from the five tion plates of the scalariform type predominate genera present in the region. Our objective was in Compsoneura, lryanthera and Otoba, wherc­ to document their full range of morphological as perforation plates of the simple type pre­ variability associated with vessel elements. Af­ dominate in Osteophloeum and Virola. The ter characterising these structures in each , phylogenetic and taxonomie implications of we consider the implications for the phylogeny these findings are discussed. and of the regional genera as a Key words: Compsoneura, lryanthera, Osteu­ group. phloeum, Otoba, Virola, Vessel perforations. Material Introduction In Brazilian Amazonia, the species of Myris­ The family Myristicaceae, widely distributed ticaceae are distributed as folIows: Compsoneu­ in tropical regions, is represented in the Brazilian ra (5), lryanthera (19), Osteophloeum (I), Oto­ Amazon region by five genera (Compsoneura, ba (I) and Virola (29) (Rodrigues, 1978, 1981, Iryanthera, Osteophloeum, Otoba and Virola) 1982). Of the 55 species in the region, 41 were and 55 species. Smith and Wodehouse (1937), examined in this study. In the genus Compso­ Ducke and Black (1954), and Rodrigues (1978) neura, only the wood of C ulei was examined considered Amazonia to be the distribution due to a lack of specimens of other species, centre of this family in the Americas. which are all rare. Specimens were obtained The idea that vessel elements in Angiosperms from the wood collections of the Instituto Na­ originated from more primitive vascular ele­ cional de Pesquisas da Amazönia (INPA) in ments known as tracheids has been weil accept­ Manaus, Brazil; the Centro de Pesquisas Agro­ ed for some time (Frost, 1930; Cheadle, 1943). pecuaria do Tr6pico Omido (lAN) and the Mu­ Through successive morphological modifica­ seu Goeldi (MG) in Belem, Brazil; the Jardim tions, vessel elements transformed into a com­ Botänico (RB) in Rio de Janeiro, Brazil; the pact type with simple perforation plates. This University of Utrecht (U) in Holland; and the general evolutionary sequence gave rise to vari­ Forest Products Laboratory (MAD) and the ous levels of specialisation that are used by Samuel Record Collection (SJR) in Madison, anatomists as a valid parameter for clarifying Wisconsin, U.S.A. the phylogeny and taxonomy of botanical groups. Material studied: Little has been published concerning the Compsoneura Warb.: C ulei Warb.: Amazo­ morphology of vessels in the Myristicaceae of nas, INPA 142, INPA 4799, INPA 8054; Para, Brazilian Amazonia. The most comprehensive MG 2346; Rondönia, MG 4108. publication is by Garrat (1933), who studied lryanthera Warb. - I. campinae W. Rodr.: the wood anatomy of the family and construct­ Amazonas, INPA 6972. - I. coriacea Ducke: ed a key to separate genera on the basis of Amazonas, INPA 786, INPA 7331. - I. crassi­ characters associated with the type of vessel folia A.C. Smith: Amazonas, MAD 15218. - I. perforation plates. Due to a lack of sufficient elliptica Ducke: Amazonas.IAN 101849: INPA material, Garrat was unable to interpret accu­ 2895, INPA 5614; MAD 14105. - I. grandis rately the occurrence of various types of per- Ducke: Amazonas, INPA 5809: Mato Grosso,

* Department of Botany, Museu Paraense Emilio Goeldi, Caixa Postal 399, 66.000 Belem, Para, Brazil. ** Instituto Nacional de Pesquisas da Amazonia, Caixa Postal4 78, Manaus, Amazonas, Brazil.

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Uw 19330; Pani, INPA 6052. - 1. hostmanni tions of acetic acid and hydrogen peroxide (Benth.) Warb.: Maranhäo, MG 2358. - 1. inpae (30% vol.) at 60° C for 24 hours. The sampIes W. Rodr.: Amazonas, INP A 5181. - 1. juruen­ were subsequently washed in running water sis Warb.: Amazonas, INPA 5430; MG 1022; and stored in beakers with water and a few Pani, SJR 22074. - 1. laevis Markgraf: Amazo­ drops of 2% formaldehyde. Prior to preparing nas, INPA 4061; Roraima, INPA 4613. - 1. lan­ slides, each sam pIe was stained with a few cifolia Ducke: Amazonas, INPA 5510, INPA drops of a safranin in a water-ethanol solu­ 5529, INPA 5926. - 1. macrophylla (Benth.) tion, and then mounted on a minimum of five Warb.: Amazonas, INPA 1005, INPA 1536, slides in glycerin. A minimum of 25 vessel ele­ INPA 3375. - 1. olacoides A.C. Smith: Rorai­ ments were examined per sampIe. ma, INPA 4401. - 1. paradoxa (Schw.) Warb.: The length of the vessel elements were mea­ Amazonas, INPA 4989, INPA 5118,INPA 5168. sured with the aid of an 01ympus projector un­ - 1. paraensis Huber: Amazonas, INPA 1992, der 100 x magnification and included the entire INPA 4461, INPA 5156. -I. polyneura Ducke: vessel length plus terminal appendices. Diame­ Amazonas, INPA 4915, INPA 5333, IN PA ters were measurcd using cross sections on all 5819, INPA 5986. - 1. sagotiana (Benth.) slides from the Museu Goeldi and INPA collec­ Warb.: Amapa, INPA 1313, INPA 1314. - 1. tions. Counting of the bars in the scalariform tessmannii Markgraf: Amazonas, MAD 22912.- plates was done using a light microscope, which 1. tricornis Ducke: Amazonas, INPA 5506; Ro­ was found to produce more clarity than the raima, INPA 4466. - 1. ulei Warb.: Amazonas, projector. INPA 1360, INPA 5021, INPA 5081. Botanical specimens corresponding with the Osteophloeum Warb. - 1. platyspermum wood sampIes were identified by Dr. William (A.DC.) Warb.: Amazonas, MG 962, MG 2758; Rodrigues of the Botany Department of the INPA 5334, INPA 6192; Para, lAN 136833. Instituto Nacional de Pesquisas da Amazönia Otoba DC. ex Karst. - 0. parvifolia (M.G.F.) (INPA), a specialist on Neotropical Myristica­ A. Gentry: Acre, IAN 133382; Amazonas, INPA ceae. 6231. The terminology utilised in this paper fol­ Virola Aublet. - V. albidiflora Ducke: Ama­ lows that adopted by the Committee on No­ zonas, MAD 14004. -- V. caducifolia W. Rodr.: menclature of the International Association of Amazonas, INPA 5577. - V. calophylla Spr. ex Wood Anatomists (lAWA, 1964). Classification Warb.: Amazonas, INPA 4750, INPA 5027, IN­ of measurements followed the Panamerican PA 6468. - V. carina ta (Benth.) Warb.: Pani, Commission of Rules and Techniques (Comision MG 1673. - V. coelhoi W. Rodr.: Amazonas, Panamericana, 1974). INPA 6200. - V. decorticans Ducke: Amazo­ nas, INPA 15427. - V. divergens Ducke: Ama­ Results and Discussion zonas, INPA 5050. - V. duckei A.C. Smith: Tables 1 and 2 summarise the morphological Amazonas, INPA 5164. - V. elongata (Benth.) characteristics of the vessel elements of the five Warb.: Amazonas, IAN 115634; Para, IAN genera of Myristicaceae examined in this study. 86303, 86353; MG 1814. - V. flexuosa A.C. The morphology reveals an extremely wide Smith: Amazonas, INPA 6189. - V. guggen­ range of forms, including vessels that are short heimii W. Rodr.: Amazonas, IAN 99848; IN PA to 10ng, narrow to wide, and with perforation 5370. - V. lorentensis A.C. Smith: Amazonas, plates located at diverse sites along the vessel RB 2854. -- V. michelii Hecke!: Amapa, MG walls, with their orientation varying from 574; Amazonas, INPA 3259; Pani, IAN 101594, slightly inclined (i. e., almost horizontal) to ver­ IAN 106978. - V. minutiflora Ducke: Amazo­ tical. The perforation plates are likewise of nas, INPA 5390. - V. multicostata Ducke: variable form, not only at the generic but also Amazonas, INPA 3231; Pani, MG 1912. - V. at the specific level. Plates of the simple, scala­ multinervia Ducke: Amazonas, INPA 3855; riform, and reticulate type are common, but Para, IAN 101597. - V. sebifera Aubl.: Rorai­ atypical types occur that appear to be a mix­ ma, INPA 4452. - V. surinamensis (Rol.) Warb.: ture of scalariform and reticulate; these were Amazonas, MG 527; INPA 710; Para, IAN named semi-scalariform. 106872. - V. venosa (Benth.) Warb.: Amazo­ Despite the wide morphological range of per­ nas: INPA 115761. foration plates within each genus, it was pos­ sible to discern apredominant type. Scalari­ Methods form plates are common in all the genera stud­ Sam pIes consisting of longitudinal slices of ied but are especially predominant in Compso­ the heartwood were obtained from each of the neura (Plate1: 1-4) and Otoba (Plate 1: 5-8); wood specimens studied. The sam pIes were although present in all the species of Iryanthera. macerated in a solution containing equal por- they only attain similar predominance in thc

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Table 1. Characters of vessel elements in Myristicaceae from Brazilian Amawnia.

I = inclined, FI = sttongly inclined, SI = slightly inclined, V = vertical. s.d. = standard deviation of the mean. For the characters simple, reticulate, semi-scalariform and scalariform plates, two values indicate the minimum and maximum within the species examined; a single value indicates that only one specimen was examined.

~ ~ '" ""'0 '-' r-.. ~ ~ § '-' r-.. -a 'J:l .~ ~ .~c:: '"0.> '" ~ ~ ~ "'0.> e Kl .,gE .!ii ~~ &!S ~ '" "'- ~"'- -"'- -ä E 'oE ~E ! ] i ~u .... .,g .~ 0 -5 ß .E::s 2'g bO bO -ä u ~ §~ c:: 'J:l öl e- e u asöl.... u ~ § 'öl ~ 'i ",-", Species '" '" 2 ~ mean ± s.d. mean ± s.d. mean ± s.d. Compsoneura ulei 1078 ± 313 39 ± 8.5 0-2 0 0 98-100 10.8 ± 3.2 FI Iryanthera campinae 982 ± 197 91 ± 3.9 0 7 0 90 5.3 ± 1.4 coriacea 1164 ± 49 57 ± 7.3 0 1 5-7 83-95 5.0 ± 1.5 FI crassifolia 1200 ± 196 100 ± 16.8 0 65 2 33 5.0 ± 1.2 elliptica 1344 ± 265 119 ± 15.9 0 7-9 0-11 73-93 4.1 ± 1.2 FI grandis 1124 ± 180 100 ± 18.8 60-74 0-1 0-7 26-33 1.3 ± 0.8 I hostmanni 1082±231 87 ± 9.1 0 80 19 5.3 ± 1.1 FI inpae 1248 ± 153 100 ± 4.1 0 5 10 86 5.5 ± 1.5 FI, V juruensis 1135 ± 167 96 ± 13.8 0 12-34 3-19 62-80 4.8 ± 2.3 FI laevis 1294 ± 185 101 ± 14.3 0 5-14 0-14 80-88 3.4 ± 1.5 FI, V lancifolia 1458 ± 223 110 ± 13.5 0 14-53 11-16 50-73 5.0 ± 1.5 macrophylla 1146 ± 169 79 ± 8.0 0 60-75 7-9 15-32 4.2 ± 1.9 olacoides 1002 ± 162 52 ± 8.3 0 4 5 91 6.8 ± 2.3 FI paradoxa 1279 ± 146 85 ± 10.7 0 11-34 3-7 58-86 5.5 ± 0.8 FI paraensis 1231 ± 160 80 ± 8.3 0 64-69 6-11 22-25 6.7 ± 2.5 FI polyneura 1263 ± 229 84 ± 14.9 0 30-35 0-5 70-95 6.1 ± 2.3 sagotiana 1178 ± 270 104 ± 16.2 0 20-40 0-10 60-80 3.8 ± 1.6 FI, V tessmannii 1203 ± 168 73 ± 10.5 0 12 4 68 7.6 ± 4.8 tricornis 1085 ± 313 110 ± 14.1 0 29 4 67 3.3 ± 1.3 I ulei 1171±174 78 ± 8.8 0 52-75 0-17 24-38 6.4 ± 2.8 FI Osteophloeum platyspermum 1407 ± 285 148 ± 37.0 83-100 0-1 0-3 3-17 3.9 ± 2.6 SI, I, FI Otoba parvifolia 1394 ± 218 152 ± 23.6 0 13-20 3-13 73-77 4.6 ± 0.9 I, FI Virola albidiflora 1176 ± 214 98 ± 21.6 77 0 0 23 1.3 ± 0.7 FI, V caducifölia 1121 ± 362 133 ± 26.8 87 0 0 13 5.2 ± 3.1 FI, V calophylla 1130 ± 230 108 ± 20.6 80-100 0 0-2 1-39 2.9 ± 1.9 I carinata 1276 ± 262 130 ± 33.6 98 0 0 2 1.6 ± 0.8 FI, V coelhoi 986 ± 211 98 ± 18.7 71 0 3 3 2.7 ± 1.9 decorticans 920 ± 264 116 ± 34.2 73 0 8 19 4.4 ± 2.9

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(Table 1 continued) '" ~ .... ]: 0 ...... , S'" '" .... '" !:l'...... , § S Cl.'" '.':l ", ~ .S ~ '0\ ~ ---~ E 8 "'(;j 8 ~ ~ ta- &$ .~ '" ~ <8 0. .00. ~o. B 0. «i '5E ~ E '" '" .~ 0 '.':l Cl. ~u ! ~ ",..... ~ -5 ß ~ 'f '!ä .0 §~ bI) bI) u 0:: '.':l .~ «i 8- ", § i u ~"§ Species - '0\ ~ '" '" a ~ 0.'" mean ± s.d. mean ± s.d. mean ± s.d. (ViroIa) divergens 995 ± 188 117 ± 29.1 64 0 0 36 3.5 ± 2.1 I, FI duckei 1200 ± 244 127 ± 31.9 91 0 0 9 3.6 ± 3 I elongata 658 ± 175 114 ± 19.3 59-94 1 0-6 6-38 2.4 ± 1.8 flexuosa 1108 ± 244 113 ± 24.1 81 0 2 17 4.4 ± 2.2 guggenheimij 958 ± 150 121 ± 21.8 90-96 0 0-1 4-9 5.5 ± 2.5 Fr lorentensis 1021 ± 168 76 ± 16.5 68 0 4 28 2.9 ± 1.8 I, FI michelii 1004 ± 245 133 ± 27 76-89 0 0-5 6-22 5.0 ± 3.7 minutiflora 1050 ± 113 109 ± 27.1 95 0 0 5 5.6 ± 3.4 multicostata 1273 ± 185 108 ± 18.7 80-88 0 0 12-20 1-7 multinervia 1056 ± 252 84 ± 11.9 0 0 0-3 13-15 5.7 ± 3.8 sebifera 1216 ± 205 96 ± 18 98 0 1 1 1.4 ± 0.7 surinamensis 1091 ± 270 113 ± 25.4 82-90 1 0 10-18 3.9 ± 2.6 venosa 1088 ± 263 76 ± 18.2 87-89 0 0 11-13 6.6 ± 2.8 FI species I. coriacea, I. elliptica, I. juruensis, I. soneura examined in this study unless they laevis, I. lancifolia, I. olacoides, I. paradoxa, J. oeeur in extremely low proportions (Iess than polyneura, J. sagotiana, J. tessmannii, and I. tri­ 1%). cornis. In Virola and Osteophloeum, sealari­ Simple plates are charaeteristie of the genera form plates are found in all of the speeies stud­ Virola and Osteophloeum. In the first these ied, but are predominant in none. plates are present and predominant in all spe­ The number of bars per plate of the scalari­ eies. In the seeond, a monospeeifie genus, simple form type is highest in Compsoneura. In the plates are present in all specimens at a frequen­ other genera examined, numerous bars per ey greater than 80%. In Jryanthera, simple plate do oecur but the average number is not as plates are predominant only in I. grandis, an high as in Compsoneura. The form of these atypieal eondition in this genus, where sealari­ bars varies from regular to highly irregular and form or retieulate plates are more eommon. In branching; their width varies from thin to Compsoneura the oeeurrenee of simple plates is thiek. Branehing bars are most eommon in insignifieant, and they appear to be absent in Jryanthera. Exeessive branching results in a Otoba. type of plate that is intermediate between scala­ The presenee of different types of plates in riform and reticulate, this type is named semi­ the same vessel element is eommon. Sealari­ scalariform beeause it originates from the scala­ form plates at one end and retieulate plates at riform type. A similarly intermediate type of the other are frequently found in Jryanthera. plate is mentioned by Sehmid and Baas (1984) In this same genus, eombinations of scalariform in their study of scalariform perforations in and reticulate, retieulate and simple, or reticu­ woods of Myrtaceae. late and semi-reticulate were also observed Perforation plates of the reticulate type are (Plate II: 4,7 & 13). most frequent in Jryanthera but only predomi­ In Osteophloeum platyspermum and Virola, nate in I. crassifolia, I. hostmanni, I. macro­ simple and scalariform plates are present in the phylla, J. paraensis, and I. ulei. They are also same vessel element. present in Osteophloeum, Otoba and Virola, but were not observed in the material of Comp- (text continued on page 210)

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Plate H.II. Vessel elements of Iryanthera,Iryanthera, all x 70. - 1: fI coriacea.coriacea. - 2-3: fI inpae. - 4: fI grandis.gran dis. _ 5: fllaevis. laevis. _ 6-8: 6- 8: fI paraensis. _ 9-11:9- 11: via freeaccess LI sagotiana.sagotiana. - 12-13: fI ulei. N No o--l-.J -.J IV o 00

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Plate IV. Vessel elements of Osteophloeum , all x 75. - 1- 7: Osteophloeum platyspermum. Note the occurrence ofvessel elements with three via freeaccess perforation plates in 1,3, and 5. N o \Cl 210 IAWA Bulletin n.s., Vol. 8 (3),1987

Table 2. Character summary ofvessel elements in the genera of Myristicaceae in Brazilian Amazonia.

S 2> ...... ' ~--- .... --- S'-' ~ ~ 0) '" 0) '" 0) .~C '"0) .", ..... S ~ 2'" ","'" c..::! ...."'~ '" :.a'" .....'"0) p.'" '" 0; .00; ---S ..::! S.... S .... '-o S.... 2> ..... 0; ~ .... 0.8 '"c 0) StE O).~ .<:: 0) "3'" °C 0i=: .0 .... bo Ol) P. ..:g..:g c c ~ S..::! Genera v .5 0) ü ü ;:l '" ~ .;:l .... '" '" C ~ '" '" '" Compsoneura (400) 1078 (1700) (20) 39 (60) 0.9 9 99.9 (4) 10.8 (24) Iryanthera (320) 1188 (1990) (40) 90 (190) 3.1 32.4 64.5 (I) 5 (16) Osteophloeum (800) 1407 (2400) (60) 148 (240) 90.3 0.7 8.8 (0) 3.9(11) Otoba (1000) 1394 (1750) (90) 152 (200) 0 16.6 83.3 (2) 4.6 (7) Virola (480) 1070 (1980) (40) 109 (190) 85.5 0.05 13.6 (1) 3.6 (22)

In several species of Iryanthera (l. grandis, I. quist (1985) and Baas (1986), have shown that hostmanni, I. juruensis, I. paraensis, I. ulei) and scalariform perforation plates are more com­ Virola (V. ealophylla, V. earinata, V. miehelii) mon in mesic or cool temperate environments an unusual condition occurs, in which three per­ whereas simple perforation plates are more com­ foration plates are found within a single vessel mon in drier environments. Despite the large element. Plate II: 6 illustrates avesseI element variation in the types of perforation plates of Iryanthera paraensis containing two plates found in Amazonian Myristicaceae, there does of normal size with scalariform perforation and not appear to bc any clear relation between the a sm aller, third plate that is circular in form. In environment and a given type of perforation Virola ealophylla (Plate IlI: 2 & 3) and Osteo­ plate. This lack of relation is not surprising in phloeum platyspermum (Plate IV: 1,3 & 5) view of the relatively uniform climatic condi­ three simple plates occur in a single vessel ele­ tions which prevail over most of the Amazon ment. Another unusual situation is the OCCUf­ Basin, despite its immense area. rence of two plates at one end of the vessel and an absence of plates at the other end. This con­ Taxonomie and phylogenetie aspeets dition is found, for example, in Virola albidi­ Various authors (Metcalfe & Chalk, 1950; flora (Plate III: I), V. earinata (Plate III: 5), and Carlquist, 1961) have recognised that the mor­ V. elongata (Plate III: 7). phology of vessel elements can serve to resolve In some cases one observes plates that di­ uncertainties concerning the taxonomy and verge from the general pattern in Myristicaceae. phylogeny of botanical taxa. In the Amazonian One example is the occasional occurrence of an Myristicaceae, the morphology of perforation extremely fine reticulate form (Plates II: 4 and plates provides a useful means of clarifying IV: 7) that is quite distinctive from the well-de­ taxonomy and evolutionary trends. fined reticulation typical of Myristicaceae. An­ Despite the presence of scalariform plates in other example was observed in Osteophloeum all of the five regional genera, it is possible to platyspermum, where an isolated bar (Plate IV: distinguish them on the basis of their perfora­ 4) occurred in a perforation plate of the simple tion plates (see Table 2). Garrat (1933) report­ type; a similar, apparently residual structure ed that no single type of perforation plate was was reported by Armstrong and Wilson (1980) eonsistently predominant in all specimens of for the Asiatic genus Horsfieldia (Myristica­ Iryanthera, Staudtia and Virola. Although the ceae) and by Giraud (1981) in Hieronyma an­ plates of the vessel elements assurne an ex­ dina (Euphorbiaceae). tremely wide variety of forms within the Myris­ In recent years, a number of publications ticaceae, this study reveals that, with rare ex­ have detected a relation between the morpho­ ceptions, a given type predominates in practi­ logy of vessel elements and the type of environ­ eallY all of the species and specimens of a given ment in which the oceur. Van den Oever genus. We suspect that Garrat's observation et al. (1981), Baas et al. (1983), Baas and Carl- may have been based on erroncous identifiea-

Downloaded from Brill.com09/29/2021 09:37:21PM via free access IAWA Bulletin n.s., Vol. 8 (3),1987 211 tion of herbarium specimens, especially since frequency of simple plates, but because its ves­ taxonomic knowledge of the family was still sei elements exhibit a relatively high diameter­ limited at the time of his study. to-Iength ratio. lryanthera grandis was the only species Siddiqi and Wilson (1974) found a predomi­ among the 41 studied that consistently diverg­ nance of scalariform perforation plates with ed from the characters predominant in its 2-9 bars in the Asiatic genus Knema, as well as genus. The absence or scarcity of simple per­ the presence of semi-scalariform and reticulate foration plates in all other species and speci­ plates. In the other Asiatic genus, Horsfieldia, mens of lryanthera seems to indicate that I. simple plates predominate in mature woods grandis pertains to another genus, probably (Armstrong & Wilson, 1980). The morphologi­ Virola. This matter is currently being investi­ cal variations reported among the Asiatic genera gated further by the senior author in a study of are quite similar to those found in the Ameri­ the wood anatomy in lryanthera. can genera. Further study of the family as a The predominance of scalariform plates in whole could shed light on relations between Compsoneura. Iryanthera and Otoba, and sim­ the Asiatic and American genera. ple plates in Osteophloeum and Virola dem on­ The precise evolutionary status of the five strates the existence of various levels of specia­ genera examined in this study requires a com­ lisation in the secondary xylem vessels. plete analysis of all morphological characters. According to Carlquist (1961), scalariform The pollen analysis of Smith and Wodehouse perforation plates are relatively primitive. (1937) indicates the following sequence of Plates of this type are present in all specimens specialisation for the American species of examined in the five Amazonian genera and Myristicaceae: Otoba, Virola, Osteophloeum, seem to constitute an ancestral character com­ Compsoneura and lryanthera. More recently, mon to all Myristicaceae. The frequency of scala­ Walker and Walker (1979, 1983) analysed poi­ riform plates is relatively low in Osteophloeum len morphology in the five American genera and Virola, high in Compsoneura and Otoba, of the Myristicaceae and. reported that Comp­ and intermediate in lryanthera. The almost ex­ soneura and Virola are closely related. Their clusive occurrence of scalariform plates with findings are not confirmed by our study of exceptionally high numbers of bars indicates vessel elements, which shows a sharp distinc­ that Compsoneura and Otoba are the most tion between these genera in predominant primitive genera of the Amazonian Myristica­ type of perforation plates and tangential diam­ ceae. Among these two genera, the vessel ele­ eter (see Table 2). On the other hand, the mor­ ments are considerably longer in relation to the phological distinctions found by Walker and diameter in Compsoneura (Tables I & 2), which Walker for the other three genera are confirm­ suggests that this genus may be the most primi­ ed by their vessel element morphology. These tive of the group. authors, however, do not discuss the possible lryanthera is the only genus that fails to ex­ relations of Compsoneura and Virola with the hibit a single predominant type of perforation other genera. The sequence of xylem speciali­ pla te. Despitc the high frequency of scalari­ sation proposed in this study, on the basis of form plates in this genus, reticulate plates are perforation plate morphology, is quite differ­ well represented in all species examined. The ent from that proposed by Smith and Wode­ evolutionary position of Iryanthera thus ap­ house (1937): Compsoneura, Otoba, lryan­ pears to be intennediate in relation to the thera, Virola, and Osteophloeum. We thus have other regional genera, yet with a predominance to concur with the statement made by Smith of primitive characters, as indicated by the sum and Wodehouse (1937) concerning Myristica­ of scalariform and reticulate plates. In addi­ ceae: 'The distribution of essential characters tion, the frequent occurrence of semi-scalari­ among the American genera is such that one is form plates, which represent a morphological unable to designate a 'primitive' genus.' transition between the scalariform' and reticu­ late types, further indicates the intermediate Acknowledgements evolutionary status of this genus. The authors would like to express their grati­ Virola and Osteophloeum exhibit a more tude to the late Dr. Francis Kukachka of the evolved status in relation to their perforation Forest Products Laboratory, Madison, Wiscon­ plates, which are predominantly of the simple sin, U.S.A., Mr. Ben l.H. terWelle of Utrecht type. Many species of Virola also exhibit sca­ University, the Netherlands, Dr. Joaquim 1. lariform and reticulate plates but at relatively Gomes of CPATU / EMBRAPA, Brazil, who low frequencies. The monospecific Osteo­ generously donated wood sampies of Iryan­ phloeum appears to be the most evolved genus thera, and Dr. Anthony Anderson, who trans­ of the group, not only due to its relatively high lated the text into English.

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