Noun:

Cycad,

cycad தமிழ் அர்த்தத்தின் உதாரணம்:

இது Cycadales என்ற பேரினத்தைச் சேர்ந்தது.

Escarpment Cycad (2006 இலிருந்து).

cycad's Usage Examples:

The endosperm detached from a large Ginkgo ovule after fertilization bears a close resemblance to that of a cycad; the apex is occupied by a depression, on the floor of which two small holes mark the position of the archegonia, and the outgrowth from the megaspore apex projects from the centre as a short peg.

Short and reticulately-pitted tracheal cells, similar to tracheids, often occur in the circummedullary region of cycadean stems.

The vascular system of cycadean seedlings presents some features worthy of note; centripetal xylem occurs in the cotyledonary bundles associated with transfusion-tracheids.

The plants of the Lower Gondwanas consist chiefly of acrogens(Equisetaceae and ferns)and gymnogens (cycads and conifers), the former being the more abundant.

In rare cases the pinnae of cycads are lobed or branched: in Dioon spinulosum (Central America) the margin of the segments bears numerous spinous processes; in some species of Encephalartos, e.

) with yucca-like leaves, was related to the cycads and conifers; the catkin-like inflorescence, which bore yew-like berries, is called Cardiocarpus.

In the genus Cycas the female flower is peculiar among cycads in consisting of a terminal crown of separate leaf-like carpels several inches in length; the apical portion of each carpellary leaf may be broadly triangular in form, and deeply dissected on the margins into narrow woolly appendages like rudimentary pinnae.

a, The main anatomical features of a cycad stern a Spermatozoids may be summarized as follows: the centre is from G of fi occupied by a large parenchymatous pith traversed g; by numerous secretory canals, and in some genera c p onen-grain by cauline vascular bundles (e.

It is interesting that no monstrous cycadean cone has been described in which ovuliferous and staminate appendages are borne on the same axis: in the Bennettitales (see Palaeobotany: Mesozoic) flowers were produced bearing on the same axis both androecium and gynoecium.

A point of anatomical interest is the occurrence in the vascular bundles of the cotyledons, scale-leaves, and elsewhere of a few centripetally developed tracheids, which give to the xylem-strands a mesarch structure such as characterizes the foliar bundles of cycads.

A thorough examination of cycadean seeds has recently been made by Miss Stopes, more particularly with a view to a comparison of their vascular supply with that in Palaeozoic gymnospermous seeds (Flora, 1904).

The mesarch structure of the leaf-bundles is met with in a less pronounced form in the flower peduncles of some cycads.

The same classes of plants occur in the Upper Gondwanas; but there the proportions are reversed, the conifers, and still more the cycads, being more numerous than the ferns, whilst the Equisetaceae are but sparingly found.

Synonyms:

Macrozamia spiralis, burrawong, ceratozamia, Macrozamia communis, Encephalartos caffer, zamia, gymnosperm, dioon, kaffir bread, encephalartos, macrozamia, Cycas revoluta, sago palm,

Antonyms:

None