In this article we will discuss about the morphology of cycas with the help of diagrams.
Cycas is a short palm-like plant (Fig. 15.1). When sterile, it bears a striking resemblance to ferns. This is accentuated by circinate vernation of its leaves. Cycas is a native of tropical and subtropical regions. It grows very slowly in woodlands and Drier Mountain slopes, exposed to the sun.
It is also cultivated in parks because of its unique beauty; thick cylindrical trunk and conspicuous crown of pinnate compound leaves. It is propagated by bulbils present on the stem, at the base. The xerophytic nature of the plant is revealed by tuberous underground stem and un-branched short aerial stem with an armour of persistent leaf bases.
Four species of Cycas growing wild in India are: C. circinalis, most abundant in deciduous forests of Western Ghats. C. pectinata that grows in sal forests of Sikkim, Assam, Khasi hills and Manipur, C. rumphii that abounds beach forests of Andaman and Nicobar Islands, and C. beddomei that is confined to the hills of Cuddapah district of Tamil Nadu and eastern Andhra.
Leaves of Cycas are dimorphic: a crown of large pinnate foliage leaves and smaller scale leaves, cataphylls. These alternate regularly. The leaves last for 3-10 years and on dropout their persistent bases cover the stem. The cataphylls are simple, about 5-10 cm long, very hairy and sharp-pointed. These completely cover the apical dome, during the periods when new crowns of vegetative leaves are produced.
Foliage leaves are unipinnate compound (Fig. 15.2A), with many thick and leathery sessile leaflets of spine tips. A single midrib runs along the entire length. The pinna margin is of taxonomic value, it is revolute in C. revoluta (Fig. 15.2A, B) or flat in C. circinalis.
Annually, two crowns of leaves are produced, one in spring and another in autumn, the two seasons of growth.
