Class Gymnospermae | Gymnosperms general characters

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This lecture is about
Class Gymnospermae
Gymnosperms are one of the successful groups of seed plants of worldwide distribution They
constitute about one-third of the world’s forests. The gymnosperms are heterosporous plants which
produce seeds but no fruits. The term gymnospermae literally means ‘naked seeded’ (Gymno=
naked, spermae= seed). The ovules in these plants are usually borne on the exposed surfaces of
fertile leaves (megasporophylls). These ovules, unlike those of angiosperms are not enclosed but
lie naked on the surface of fertile leaves.
Like Filicinae, they show regular heteromorphic alternation of generations. They have independent,
dominant sporophyte but less conspicuous, dependent gametophyte. The female gametophyte is
permanently retained within the ovule. The two kinds of spores are microspores and megaspores
which develop on microsporophylls and megasporophylls respectively. The megasporophylls
bearing ovules are not folded and joined at the margins to form an ovary. For this reason the seeds
lie naked on the mega sporophylls, (Fig. 9.20a).
The important genera are Cycas (sago-palm) (Figs. 9.20-a), Pinus (Pine), Taxus (Yew), Picea (Hemlock)
and Cedrus (deodar) Ginkgo