THE CLASSIFICATION OF GYM~ OSPERMO S PLANTS DIVYA DARSHA'[ PANT Botany Department, The University, AHahabad ABSTRACT But soon after the discovery of motile sperms in thi:i genus (HIRASE, 1896), Engler ( 1897) Various systems of classification of the gymno­ spermous plants are briefly reviewed. Arnold's created a special cla.· , the Ginkgoales for classification (Bot. Gaz.. 1948) is tentatively Ginkgo and its fossil representatives. By the modified as follows: beginning of the present century the knowl­ Division: Cycadophyta ­ Class 1. Pterictosper­ edge of three more types of fossil gymno­ mopsida. Order:;: 1. Lyginopteridales. 2. Mec\ul­ losales. 3. Glossopteridales. 4. Peltaspermales. spermons plants had also become sufficiently S. Corystospermales. 6. Caytoniaks. Class 2. Cyca­ clear and had led to the establishment of dopsida. Order: 7. Cycaclales; Class 3. Pentoxylo­ three more class.s, the Cordaital s, the psida, Order: 8. Pentoxylalcs; Class 4. Cycadeol­ Pteridosperm:i and the Bennettitales. Engl r deopsida, Order 9. Cycackoicleales. Division: Chlamydospermophyta - Class Gneto­ ( 1897 ), Coulter & Chamberlain (1917) . psida. Orders: 1. Gnetales (restricted to Gnetum). Engler & !'rant! ( 1926), H.endle ( 1930) and 2. Welwitschiales. others all recognize the Gymnosperms a pri­ Division: Coniferophyta - Class 1. ConiIcro­ mary division of the Spermatophyta-Phane­ psicla, Orders: 1. Cordaitales. 2. Ginkgoales; 3. Coniferales; Class 2. Ephedropsida. 4. Epheclrales; rogamia or Embryophyta - Siphonogama. Class 3. Czekanowskiopsicla. Order: S. Czekanows­ They then directly divide the group into kiales; Class 4. Taxopsida. Order: 6. Taxales. classes or orders of co-ordinate rank, viz. The position of the Pentoxylales, Ephedrales. (1) Pteridospermae (or Cycadofilicales), Glossopteridales and Czekanowskiales is discussed in the light of recent research. (2) Cycada1cs, (3) Bennettitales, (4) Cordai­ tales, (5) Ginkgoales, (6) Coniferales, and (7) Gnetales INTRODUCTIO In contrast, Berry (1917) divides the The history of gymnosperm classification gymnospermous plants into the Pterido­ begins with the year 1827 when Robert spermophyta, Cycadophyta and Conifero­ Brown recognized the naked seed of the phyta without classing them as Gymnosperms. Cycads and the Conifers. and called them Gymnosperms. Later, Endlicher (1836­ DEVELOPMENT OF PHYLOGE. ETIC 1840) gave them the same rank as the SYSTEMS three divisions of Dicotyledons under his Acramphibrya, Adolphe Brongniart ( 1843 ) In 1919, Sahni (1920) for the first actually included them in the Dicotyledons time clearly recognized two main phyletic and Bentham & Hooker ( 1862-1883) placed lines in the orders of the G mnosperms: them between the Dicotyledons and the (1) the Phyllo.-perms consisting of (a) the ~10nocotyledons. ltimately, Hoffmeister's Pteridospermae, (b) the Cycadalcs and prob­ epoch-making work ( 1851 ) on the develop­ ably (c) the Bennettitales, and (2) the ment and embryology of diverse plants led Stachyosperms consisting of (a) the Cordai­ Van Tieghem ( 1898) to remove them from tales, (b) the Ginkgoales, (c) the Coniferales, this intermediate position and he installed and (el) the Taxales (separated from tIle Coni­ them as one of the two primary divisions of f'rales and including Tax%s, Torreya and the Spermatophyta1 Cephalotaxu,s). As their names indicate, the Bentham & Hooker (1862-1883) recog­ ovules of the Phyllosperms are borne on nized only three orders of the living Gymno­ leaves or regarded to be so, while those of the spermae, viz. Gnetaceae, Coniferae and Cyca­ Stachyospc:rms are helieved to be stem­ 2 daceae. The genus Ginkgo was in those days borne . Besides the differences Jl1 the traditionally included in the Coniferae, e.g. nature of the ovule-bearing organs, Sahni it was included by Eichler ( 1889) in Taxeae along with Taxus, Torreya and Cephalotaxus. 2. This difference between the morphological nature of the ovule-bearing organ:; o( Cycads a.nd 1. The term Spermaphyta which is sometimes Conifers was first pointed out by Strasburger used is etymologically incorrect. (1879 ). 65 66 THE P,\LAEOBOTANIST also pointed out the differences between the berlain's names3 . The acceptance of Cham­ generally large and much-divided leaves berlain's nomenclature for the two lasses of the former and the simple leaves of of Gymnosperms is, however, not against the latter. Subsequently, Margaret Henson Sahni's recognition of the two main phyletic ( 1921) suggested that Sahni's two main lines in this group, only the basis of their lines may have been totally distinct and distinction is different. she associated the Stachyosperms with the Another feature of Sahni's classification Sphenopsida and the Phyllosperms ,vith which seems to have come to stay is the sepa­ the ferns. ration of Taxus and its allied forms from Almost simultaneously with Sahni, Cham­ the Coniferales and their inclu ion in a new berlain (1920, 1935) also recognized two order, the Taxalcs. Florin ( 1948) has sub­ main groups among the Gymnosperms and sequently upheld Sahni's separation of the called them by the old names Cycadophyta Taxales as an order of co-ordinate rank with and Coniferophyta, Although the composi­ the Cordaitales, Ginkgoales and Coniferales tion of Chamberlain's Cycadophyta is the ( restricted), but he includes only Taxus, same as that of Sahni's Phyllosperms and Torreya and three other newly discovered that of his Coniferophyta essentially similar genera (Nothotaxus, A mentotaxus and A us­ to Sahni's Stachyosperms (except that trotaxus) in the group retaining Cephalotaxus Chamberlain also includes the Gnetales in wi thin the Coniferales, the Coniferophyta ), yet the emphasis on the The enigmatic Gnctales have been left out primary characteristics in the two classifica­ in a doubtful position by Salmi while Cham­ tions is different. berlain includes them in the Coniferophyta The main basis of Salmi's classification is but without connecting them to the other the morphological nature of the ovule-bear­ coniferophytes (see CHAMBERLAIN, 1935, ing organs. As Scott ( 1923) pointed out p, 4, FIG. 2). Pulle ( 1938) included them soon after Sahni proposed his scheme, it was in a separate class, the Chlamydospermae, mainly a theoretical distinction for some of which is made co-ordinate with his other the groups, e,g, the Cordaitales, Bennetti­ classes of seed plants, viz, Pteridospermae, tales, and Conifers, Schoute ( 1925), who first Gymnospermae and Angiospermae. The showed that the ovule in Cordaianthus was customary inclusion of the three genera attached on a lateral appendage, pointed out Ephedra, Welwitschia and Gnetu11'~ in the that this did not support Sahni's division of single order Gnetales has also become ques­ the Gymnosperms into the Stachyosperms tionable in view of the contributions of and the Phyllosperms. Since then Florin's Pearson ( 1929), Florin ( 1931, 1933, 1934), extensive work ( 1938-45, 1951) on the stro­ Eames ( 1952) and others. Arnold ( 1948 ) bili of both Cordaitales and Conifers has made proposed the separation of Ephedra in a it abundantlv clear that the ovule in both separate order, the Ephedrales, Eames these groups" is borne on the lateral append­ ( 1952) goes further and suggests that the age of a short axis. Florin does not pre­ Ephedrales are nearest to the Cordaitales and cisely state the nature of the ovulate organ, the Coniferales and rather widely separated but the fact that he often refers to it as a from Gnetttm and Welwitschia. He also sug­ megasporophyll suggests that he regards it gests the cff~ation of two separate orders, as a foliar structure, No doubt he compares Gnetales restricted to Gnetum and WeIwits­ it with a telome, but even foliar structures chiales for Welwitschia. are fundamentally telomes, Eames ( 1952 ) In a new classification of the Gymnosperms, has already pointed out that the stachyo­ Arnold (1948) suggested that the terms spermous character of the Cordaitales and the Spermatophyta and Cymnospermae could not Conifers cannot stand, indicate natural relationships mainly because Chamberlain ( 1920, 1935), on the contrary, they are based on single characters. He emphasizes mainly the factual details of the emphasized the differences between the differences in habit, stem anatomy and leaves Cycadophyta, Coniferophyta and Chlamydo­ of the two groups. The names chosen by spermophyta (Pulle's Chlamydospermae) Chamberlain are also non-committal. Ac­ and in his classification raised them to the cordingly, despite the slight priority of the names proposed by Sahni orne recent authors, 3, Takhtajan (1953), however, retains Sa-hni's e.g. Arnold (1948), Engler, Melchior & nomenclature and Lam (1950) extends the cI is­ Werdermann ( 1954), have preferred Chal1l­ tinction even into the Angiosperms. PAXT THE CL.\.SSIFIC:\TION OF GYMNOSPERMO S PLANT 67 status of classes equal in rank with his They have incorporated s me of the features Pteridophyta (ferns only) and Angiospermo­ of Arnold's classification, but have introduced phyta under the division Pteropsida. In the following changes: addition to the separation of the Ephedrales 1. The name Gymnospermae is reincor­ (see above) under his Chlamydospermo­ porated as a division of the plant kingdom phyta he accepted the separation of the co-ordinate with the Bryophyta, Pterido­ Taxales under the Coniferophyta. He reject­ phyta, Angiospennae and others. ed the names Spermatophyta and Gymno­ 2. Two class names have been changed spermae as terms which had" outlived their to Cycadopsida and Coniferopsida,