An introduction to gymnosperms, cycas, and cycadales by Pant, D.D. and Osborne, R. and Birbal Sahni Institute of

By Pant, D.D. and Osborne, R. and Birbal Sahni Institute of Palaeobotany

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All after Long, 1960a). furnished by Xenotheca devonica, Hydrasperma tenuis from Ireland and Archaeosperma amoldii (Fig. 1F). Similar more evolved Carboniferous seeds include Genomospe rma latens (Long, 1961) w here the integumentary lobes are fused up to two thirds of their length from the base and free above (Fig. 5B-E). At the distal end of the seed the integumentary processes coalesce to form a rudimentary composite micropyle. In Salpingostoma dasu (Gordon, 1941) the integument is composed of five or six lobes which are fused up to about half of their length (Fig.

ORIGIN AND EVOLUTION OF SEEDS AND CUPULES Against such "incipient pollination" which is sometimes met with in diverse pteridophytes the actual phenomenon of pollination seems to have come into play only after the evolution of seeds. In forms like Genomospenna kidstonii and other primitive seeds, which lack a well formed micropyle, the tip of the nucellus forms an elaborate salpinx-Iagenostome for catching and lodging pollen for germination. Peroaps it was secreting a pollination drop and holding it out to catch pollen grains floating in the air as in modem gymnosperms.

9), which is possibly a pteridosperm and Maheswariella bicornuta (Pant & Nautiyal, 1963a) of uncertain affinities, the distal ends of the two sterile integumentary telomes are still free and project upwards in the form of two lateral horns. Possibly the integument of the anatropous seed of Buriadia heterophylla (Pant & Nautiyal, 1967) was formed from a forked appendage (like the forked leaf of Buriadia) where one lobe bore a megasporangium and the other was sterile. CADALES s 0 Later the megasporangium and the sterile appendage became laterally recurved on the stalk so that the megasporangium became placed between the stalk and the sterile lobe.

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