The Floral Morphology and Phylogeny of the Amentiferae
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BOTANISKA NOTISER SUPPLEMENT VOL. 2:i Utgivare: LUNDS BOTANISKA FÖRENING Redaklör // WE1MARCK STUDIES ON THE FLORAL MORPHOLOGY AND PHYLOGENY OF THE AMENTIFERAE BY HA K O N HJE L MQ VIS T DISTRIBUTOR: ( W. K (.l-KKIUI', 1-ÖHI. \(., I.LM) Introduction. The group Amentiferae, which consists of a scries of orders related to one another hut seldom regarded as a special laxonomical unity, is of a great systematical interest. According to one school of scientists, among the foremost names of which ENGLER and RICHARD WETTSTEIN may he mentioned, the Amentiferae belong to Ihe most primitive of all Angiosperms: it is thought that this group, or in any case the larger unity to which it helongs. forms the transition from the Pteridophyta or the Gymnosperms to the Angiosperms. Another school, founded by BFNTIIAM and HOOKER and especially adhered to in England, regards the Amentiferae as reduced descendants of higher organized types; their simple flower structure, according to this school, is not an original feature but a secondary character resulting from reduction. Accordingly, the group is placed high in Ihe system. There are, thus, two quite different opinions on Ihe systematical position of the Amentiferae, and. according as the one or Ihe other is adopted, quite a different picture is received of Ihe whole system and the origin ol the Angiosperms Our view of the Amentiferae is to a great extent decided by how we interpret certain morphological condilions in the flower structure, and it is therefore an important purpose of research lo elucidate these. Another matter of importance is Ihe clarification of the affinities and evolutionary lines within the group itself, among its different lower systematical units: it will thus he easier to bring it in relation to other groups. The present study is an attempt to elucidate the affinities of the Amentiferae on the basis ol morphological investigations, especially of the flower. Most of the earlier investigations made into Ihe floral morphology of the Amentiferae are rather old, dating from the latter half of Ihe 19lh century or the beginning of the 20th century. In recent times, however, valuable contributions have been made to the knowledge of the flower morphology of Ihe families in this group by American (i scientists (FiSHEB, 1928: ABBE, 1935 and 1938; ABBE and EABLE, 1940; MANNING, 1938, 1940), who have generally made combined anatomical and morphological analyses. These investigations have been of great value for the present study. Some families te.g. Fagaceae), however, have not been the subject of any such thorough analysis - they will here be treated in greater detail —, and it may also be of value lo give a comparative account of the whole group, laying stress upon the characters important for judging its systematical position. In concluding this work I wish to express my great gratitude to all the persons and institutes — Botanical gardens and museums — which have given me aid in the procurement of material or in other ways. Especially 1 thank my Chief at the Systematical Department of the Botanical Institute of Lund, Professor HERIBERT NILSSON, for his interest and benevolence. My thanks are also due lo the heads of the botanical museums in Geneva (Conservatoire et Jardin Botaniqucs), Paris (Museum National d'Histoire Naturelle, Laboratoire de Phanero gamic!. Kew iR. Botanic Gardens), Edinburgh iR. Botanic Garden), Copenhagen. Arnold Arboretum, and Washington (U. S. National Museum) for having provided me with opportunities of studying material difficult to procure. The range of the group. To Ihe group Amentiferae belong in the first place tour orders: Juglandales, Fagales, Betulales, and Salicales. The delimitation of these orders varies: thus Ihe Juglandales are often divided into two orders. Myricales and Juglandales, and the Betulales have hitherto always been united with Fagales. Still, there is no doubt that Ihe plants belonging lo Ihein are related to each other. They constitute a large natural group. To this group, however, some syslemalisls have referred, with more or less hesitation, some other small orders. One of these orders is Julianiales, with the family Julianiaceae. Already when HEMSLEY il'JOS) proposes Ihe family, he advances as his opinion thai il is related to Cupuliferae (Fagaceae), and places it between Ibis family and Juglandaceae; to the latter family il is in his opinion not closely related, lie also points out, however, Ihe existing similarities with the family Anacardiaceae, in Ihe anatomy as well as in Ihe embryology. HALLH:H I 1908) unites Julianiaceae with Anacardia ceae, but al Ihe same lime he also refers the Juglandaceae lo Ihe family, Terebintliaceae, wherein he makes Ihese and some others he merged; he is then of Ihe opinion that there is a close relationship between Juliania ceae and Juglandaceae, and also regards the other amenliferous plants as reduced descendants of the family Terebinthaceae. Following HEMS- LEY A. ENOLEB (1909) and several other authors after him have- made the famil\ Julianiaceae a special order. Julianales or Julianiales, among ihe Amentiferae. WETTSTEIN (1935) goes so far that he refers ihe family to the same order as Juglandaceae, Juglandales. On the other hand, e.g. NAGEL (191 1) in his thorough investigations of Ihe Juglandaceae has come to the opinion that, they are not at all related to Julianiaceae. As a mailer of fact, much speaks for the correctness of this view and for the Julianiaceae not being at any rate closely related to Ihe Amenti ferae, to which group I hey therefore arc not lo be referred. As early an observer as HEMSLEY stated that the family differed 8 anatomically from Juglandaceae and resembled Anacardiaceae. The more recent investigations of KRAMER I 1939.1 have confirmed this fact; this author finds a great agreement with Anacardiaceae, none with Juglandaceae. Emphasis is perhaps to he laid especially upon the occurrence of resin ducts in the stein, which are entirely lacking in the latter family bid are present in the former. The occurrence of a »cupule», an involucre that surrounds the fruits, has been considered to show the affinity ot Julianiaceae with the Amenlifeiae, where cupule-slructures also occur. The cupule is ixi Julianiaceae formed of coalcsccnt bracts, which surround 3—4 female flowers, although only in one or two of these is fruit developed. A cupule. originating from leaf-structures, is also to be found in Jug- Irmdaceae. Here, however, each flower is surrounded by a cupule. Within Fagaceae it occurs that several flowers are surrounded by a single cupule, hut this is here a stem- and not a leaf-strucfture, and, moreover, it is no doubt derived from a primary type with one cupule round each flower; such a development is no I indicated by any known facts in Julianiaceae. Further, in the latter family there are some special peculiarities without correspondence in the Amentiferae: the narrow edges of the fruits are adnate to the inner wall of the cupule and the stalk of the cupule is often broad and winged. The male flowers of the Julianiaceae have a simple perianth, of much the same appearance as in Fagaceae, but they show an important deviation from the flowers of the Amentiferae, a fact thai seems never to have been emphasized. In Julianiaceae the stamens are distinctly alternating with the perianth leaves. In Amentiferae, on the contrary, they are typically superposed; sometimes by splitting they become more than the perianth leaves, and then partly also alternate with them, somelimes there is no clear relation between perianth lobes and slamens, but only alternating stamens are a feature that is foreign to the Amentiferae. Thus, in the author's opinion, the similarities that exist between Julianiaceae and the Amentiferae are a result of secondary convergence, and there is no real affinity between these groups, at any rate no near affinity. Julianiaceae should instead most likely be placed in the proximity of Anacardiaceae. A second order that often is attributed to the Amentiferae is Bati- dales, consisting of the family Batidaceae, with the monotypic genus Batis. In placing the order VAN TIKGHKM I 1003j is generally referred to. who has carefully investigated the systematically important charac- 9 ters. The male flowers have no perianth, but arc surrounded by a cup-like leaf, at first close, later on irregularly bursting, according to VAN TlEGHEM an adossate bractcole, which at the lop has a crest-like appendage. Further alternating with the stamens there are four diagonal scales, long-stalked, spatulate, according to VAX TlEGHEM arising as emergences from an exlra-staminal disc. In the female flowers, also without perianth, there is a four-chambered ovary, which however, as VAN" TlEGHEM has pointed out, is composed of two transverse carpels and originally has two chambers, each of which is again divided into two by a false partition. The number and position of the carpels is thus the same as in many of the Anientiferae; false partitions not infrequently occur also there, and the scales of the male flowers might have a correspondence in Ihe disc-structures that occur in Salicaceae. The divergences, however, are also great; adossate bracteoles of the peculiar structure that is to be found in Batis do not occur in the Ament i ferae, and the scale-like structures have quite another shape and position than Ihe glands of Salix. VAN TlEGHEM himself, in facl, did not refer Batidaceae to some group Amentiferae, bid he placed Ihe family in his order Piperalex, between Salicaceae and Liqnidambara- ceae; thus, he connected it not only with Salicaceae, but also with several families thai do not belong to Anientiferae. On account of ils peculiar characters the family is difficult lo place in the system, having, as many authors affirm, an isolated position.