Observations on the aquatic vegetation of Trivandrum, Kerala.
The present paper deals with a survey of aquatic vegetation of Trivandrum with special reference to the growing menace from weeds especially Salvinia molesta. The distribution of the free floating plant population in low-lying areas during monsoon is discussed; this accounts for the widespread occurrence of such species as Salvinia, Azolla pinnata, Pistia stratiotes and Eichhornia crassipes. A gradual decline in population of all these except Salvinia was noticed. An account of the extent of damage caused by Salvinia is given. A method for saving the paddy crop from S. molesta by keeping wire retaining nets at the inlets and outlets of water channels in paddy fields and periodical manual removal is recommended as an important method of control. From summary.