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THE FORMATION OF LEAF-BLADDERS 

 IN E1CHHORNIA SPECIOSA, KUNTU, 

 (WATER HYACINTH) 



BY 



P. S. JlVANNA KAO, M.A. 



Agricultural College S'-Besearch Institute, Coimbatore. 



General : — Bladders in plants are comparatively rare and where 

 fchey occur, they are of doubtful significance in most cases. The best 

 known instances where such structures are conspicuously seen are 

 Sargassum, Fucus, Nercocyslis among the Fucaceae, Trapa (Onagracea?) 

 species of Utricularia, and Eichhornia speciosa (Pontederiacea?). 

 Except in Utricularia where the bladder has been definitely proved 

 to be an insect-catching and insect-preying organ, the functions 

 of the bladders have been generally supposed to be either to serve 

 as floatative or swimming organs or to serve as air reservoirs. In 

 most of the above examples the ecological value has been better 

 known rather than the physiological cause, and the present investiga- 

 tion was undertaken purely from the latter point of view. It applies 

 only to Eichhornia speciosa, a study of which was made in the 

 Botanical Laboratory at the Agricultural College and Research 

 Institute, Coimbatore, where the weed attracted notice in connection 

 with the proposed legislation for eradicating it in certain parts of the 

 Madras Presidency. 



Though Eichhornia is a water plant it thrives in such a variety 

 of situations that observers have differed regarding its exact habitat. 

 Kerner (7) for instance, states that the plants are not fixed in the mud 

 beneath the water by roots but float freely on the surface of the 

 pond. He further characterises Eichhornia as a swimming plant distin- 

 guishing it from floating plants like Trapa which are held fast to 

 the muddy bottom beneath by means of roots. Schonland (10) on 

 the other hand describes it more correctly as either swimming 

 entirely and free on the water or rooting in shallow water in 

 mud, the leaf stalks in the former case becoming strongly swollen and 

 functioning as swimming bladders. Without seriously contradicting 

 these authors it may be stated that plants with and without 

 bladders are found in deep water the determining factor for bladder 

 formation being, as will be seen below, not the depth but a plentiful 

 supply of water that is physiologically available. The plant is also 

 not restricted to any particular surrounding but is at home in ponds, 

 tanks, old wells, ditches, in marshy areas and in fact in any stagnant 



