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Morphology and Affinities of Glossopteris

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Morphology and Affinities of Glossopteris MORPHOLOGY AND AFFINITIES OF GLOSSOPTERIS K. R. SURANGE & SHALLA CHANDRA Birbal Sahni Institute of Palaeobotany, Lucknow-226007, India ABSTRACT Reproductive organs of glossopterids, viz., Eretmonia, Glossotlleea, Kendos• trobus, Lidgettonia, Partlla, Russangea, M ooia, Rigbya, Denkania, Venustostrobus, Plumsteadiostrobus, Dietyopteridium and Jambadostrobus are briefly described. Their morphology and affinities are discussed. In the Permian of the southern hemis• phere atleast two distinct orders of gymnosperms, viz., Pteridospermales and Glos• sopteridales were dominating the landscape. genera bore sporangia terminally on ultimate GLOSSOPTERISAustralia were firstleavesrecordedfrom Indiaby Brong•and branches whereas the third genus bore niart in 1828. From 1845 to 1905, sporangia crowded on a cylindrical axis. a number of new species of Glossopteris were discovered from different continents of Eretmonia Du Toit Gondwanaland. From 1905 to 1950 there PI. 1. figs. 3,4; PI. 2, fig. 2; PI. 3, figs. 2,3 were only a few records, but from 1950 onwards Glossopteris again attracted the Fertile scale leaves of Eretmonia (see attention of many palaeobotanists. At first, Chandra & Surange, 1977, text-fig. 1) are of Glos90pteris were regarded as ferns but different shapes and sizes and five species later they turned out to be seed .plants. have been recognized on this basis. The In recent years our knowledge of the fertile bracts are ovate (E. ovoides Surange reproductive structures of glossopterids has & Chandra, 1974), spathulate with acute increased to such an extent that one can apex (E. hingridaensis Surange & Mahesh• get some idea as to what type of plants wari, 1970), triangular (E. emarginata they were. Chandra & Surange, 1977), diamond-shaped (E. utkalensis Surange & Maheshwari, 1970) HABIT and orbicular (E. karanpurensis Surange & Maheshwari, 1970). The sporangia are of Glos"opteris were deciduous plants is evi• Arberiella type and produced two winged dent from the abundance of isolated leaves spores. found in the Permian deposits of Gondwana• The venation pattern in fertile scales of land. Many believe that Vertebraria were all species is almost the same. There is roots of the trees bearing Glossopteris leaves. no midrib but a few prominent bundles They were undoubtedly arborescent plants from the stalk enter the lamina and give out and many petrified woods described from secondary veins, which branch two to three Gondwanaland perhaps represent their stems. times, anastomose and form meshes as in Growth rings are common in the fossil Glo"sopteris leaves. In all species of Eret• woods which point to prevailing seasonal monia net venation is clearly seen. growth periodicity. It is also certain that The fertile scales are stalked and after male and female reproductive organs were shedding the spores, the stalks get detached borne on different plants as in other groups from the bract lamina. One pedicel arises of gymnosperms. from the stalk which divides into two equal daU!~hterbranches. Each branch then suc• MALE REPRODUCTIVE ORGANS cessively divides by repeated dichotomy and the ultimate branches bear one sporangium Three types of sporangia bearing organs each at their tips and form a sporangial have been recognized under three different cluster. Thus two sporangial clusters are genera, viz., Eretmonia Du Toit, Glossotheca borne on one pedicel of one fertile bract. Surange & Maheshwari, 1970 and Kendostro• The sporangia are oval to elliptical with bus Surange & Chandra, 1974. The first two fine parallel lines on the sporangial surface 509 510 THE PALAEOBOTANIST and are of Arberiella type. Detached Arbe• mizes immediately into two stout daughter riella type of sporangia are very common branches as in Eretmonia. Each branch in the Permian deposits of Gondwanaland. then further divides by repeated dichotomy Although, they look similar externally, it is so that possibly eight clusters of sporangia quite likely that each species contain dif• are formed on a single fertile scale. Sporan• ferent type of spores. In two cases, one gia are attached on the tip of the ultimate of the sporangium contained two winged branches and they are of striated Arberiella Faunipollenites type of spore and other type. The branching pattern of the pedicel contained Striatites type. is similar to that of Eretmonia. From the Most of the fertile scales are convex on size of the pedicels and their branching, one side and concave on the other. It is each cluster may contain not more than also thick in the middle and thin at the 32 sporangia. The sporangia are elliptical, margin. It must have acted as protective oval and striated. Although, they look alike cover to sporangial clusters which were externally, they differ in size and perhaps borne in its axil. Frequently detached in some other structural details and may sporangia are found preserved on the lamina have contained different types of spores. of the fertile scale. At maturity the sporan• At present very few carbonized sporangia gial clusters must have opened out enabling have been worked out (Chandra & Surange, the sporangia to shed their two winged 1977). The outer cells of the sporangium spores. wall are thick-walled, more long than broad It is true that Eretmonia has not been and twisted in various ways. These found attached to a Glossopteris leaf. But thickened cells give a striated appearance there is hardly any doubt that Eretmonia to the sporangium so characteristic of type of male reproductive organ belongs to Arberiella. There is also a delicate layer of glossopterids. The fertile bracts of Eret• elongated cells. Sometimes spore mass is monia are in no way different from fertile seen covered with a tissue with extremely bracts of other reproductive organs assigned thin-walled cells. The sporangium, there• to Glossopteridales (Surange & Chandra, fore, appears to be multilayered and the 1975). Moreover, Glossopteri51-like net vena• dehiscence is perhaps longitudinal. tion of the fertile bracts and their constant Isolated striated sporangia have been association with Glossopteris leaves further placed under the form genus Arberiella (Pant indicate their relationship with them. & Nautiyal, 1960). They are assigned to Eretmonia, Glossotheea and also to Pteruehus. Glossotheea Surange & Maheshwari Such sporangia have also been found attach• PI. 1, figs. 1, 2; PI. 3, fig. 1 ed to two rounded concave discs (attachment is different from Eretmom·a & Glossotheea). This genus has three species and is known There is, therefore, no doubt that the from India. It is on the same pattern as similar looking striated sporangia belonged Eretmonia but differs from it in possessing to diverse plants. Arberiella type contain more than one sporangia-bearing pedicels. two winged spores. A. afrieana contains All the three species are distinguished by Faunipollenites type of spores and A. their distinct fertile scales (see Chandra & vulgaris contains Lunatisporites type. Other Surange, 1977). Glossotheea utkalensis (Su• striated pollen grains found in masses inside range & Maheshwari, 1970) has a spathulate the sporangia have not been identified with type of bract lamina with a long and stout genera of dispersed spores. stalk, G. orissiana (Surange & Chandra, 1974) has a rhomboidal bract and a short Kendostrobus Surange & Chandra stalk and G. 1·mmani51(Chandra & Surange, PI. 3, fig. 4- 1977) has a bract large in size, oblanceolate with a short broad stalk. In G. orissiana This male reproductive organ is organized and G. immanis four slender pedicels arise on a different pattern. It is a long, narrow, on the abaxial side of the stalk one below cylindrical, cone-like organ, bearing sporan• the other in a single row, some of them gia. The cylindrical sporangia-bearing axis look as if arising from the midrib region possesses very small, round protuberences of the bract lamina. In G. utkalensis three on which 4 to 5 sporangia are attached in pedicels are seen. Each pedicel dichoto- whorls. The whorls of sporangia in theiv SURANGE & CHANDRA - MORPHOLOGY AND AFFINITIES OF GLOSSOPTERIS 511 turn are carried on the axis in close spirals oblanceolate, spathulate-Ianceolate or ovate• and appear crowded on the cone surface. lanceolate, contracted at the base into a The sporangia are large in size, one whorl long stalk. The veins spread out from the occupyi~g almost the entire breadth of the base of the lamina, those in the middle cone aXIs. running straight upwards and the rest fork The sporangia are exannulate, oval to and form anastomes right upto the margin. elongate and the sporangial surface is Cupules or cupulate discs are attached in studded with oval to round depressions, two longitudinal rows by pedicels, arising giving it a spongy appearance. This type from the abaxial surface of the basal part of sporangium in detached condition is of the lamina. In Indian species, they described under a form genus Lithangium number eight, but Lacey et al. reported (Pant & Nautiyal, 1960). The spores are 4-14 cupules. There is, however, some stripped and monolete. Unmacerated spores differences in the interpretation of the ovule show sculptine which is folded into curved bearing structure, due obviously to the ridges which are seen as longitudinal stripes imperfection of preservation. Lacey et al. in macerated spores. interpreted them as cupules, 4 to 14 in num• The mode of attachment of sporangial ber, open campanulate, sometimes appearing whorls in close spirals is something like that semicircular when compressed laterally or of seeds
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