The strobilus was axillary and bisporangiate whorls
Order Bennettitales (Cycadeoidales) : The members occur only in fossilized forms. The stem was tuberous or erect, cylindrical was and branched or unbranched. It surrounded by persistent leaf bases. The vascular system was siphonostelic and endarch. Growth rings were absent in the wood. The leaves were arranged in whorls at the tip of the stem.
The strobilus was axillary and bisporangiate. The dicotyledonous. Eg. Bennettites,Williamsonia etc. Order : Cycadales : Members of the order are commonly known as Cycades. They originated from the seed ferns. The order includes 9 living genera and about 100 species. They are woody trees, except Zamia pygmia. The stem is unbranched and is covered by persistent leaf bases.
The leaves are pinnately compound and are arranged in whorls at the apex of the stem. The leaf traces are direct as well as girdle type The wood is manoxylic. The male cone produces microsporophyills and female cone produces megasporophylls. The pollination is anemophilous.
Eg. Cycas, Zamia, Macrozamia, and Bowania are some living members. Pterophyllum and Androstrobus are some fossil Cycads. Division II. They were the dominant part of the vegetation in the Carboniferous period. The leaves were large (megaphyllous), frond- like and pinnately compound.
The primary xylem was mesarch. on leaves. Examples Calymopitys. Lyginopteris, Medullosa.Order : Cycadofilicales: All the members of Cycadofilicales are fossils, and commonly known as seed ferns. They form a connecting link between living cycads and ferns.
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