REPORTING IN SITU APOGAMOUS ABORTIVE EMBRYOS WITHIN MEGASPORES OF SOME SPECIES OF ISOETES FROM RAJASTHAN

摘要

Thin serial sections through the megasporangial portions of the four species of Isoetes from Rajasthan namely - I. coromandelina, I. tuberculata, I. reticulata and I. rajasthanensis, show distinct three layers of the wall of trilete megaspores. Both functional (fertile ) and sterile spores occur intermingled in a megasporangium. A fertile megaspore has 'spore content' wliile the sterile one is empty. The spore content either fills completely the spore cavity or it reduces and changes to U or C or a triarch structure. Free floating nucleated and enucleated cells are visible in the spore content. Some of the nucleated cell/cells make apogamous abortive embryos which are of different shapes and sizes. Circular cavity or cavities and rhizoids are also visible in many of the embryos. Archegonia are not yet seen in the sections of the megaspores. This paper includes the detailed report of apogamous, abortive embryos in situ inside the megaspores of Isoetes.