XVI International Botanical Congess

Podostemaceae is a large family of 46 genera and 260 species distributed over tropical and subtropical belt. Podostemads grow attached to rocks and boulders in gushing waters of river and waterfalls. The plant body is generally thalloid and attaches itself to the substratum by means of rhizoids and haptera. The thallus bears short vegetative shoots on the dorsal margin, which get replaced by floral shoots during the reproductive phase. Whether the thallus is of shoot or root origin has been a subject of much discussion. In this paper I communicate my findings on the origin, development and nature of thallus in a few Indian Podostemads. The structural complexity of the thallus, the manner and the origin of vegetative and reproductive shoots has also been examined. The information drawn is then compared with existing literature. The possible adaptive and evolutionary significance of the thallus will be discussed.l