312 THE JOURNAL OF INDIAN BOTANY. 



Of these stages the first is quite commonly observed in pools and 

 streams ; the second is not well represented ; the third is the present 

 modified climatic climax ; stage four is not found well developed 

 anywhere, but fragments of it are to be seen in protected places, 

 and in the thorny shrubs and small trees scattered over certain 

 areas ; stages five and six are largely hypothetical, and six would 

 be the true climatic climax for this portion of the Gangetic Plain. 



Aquatic stage. As has been said, the aquatic stage is to be 

 found in the numerous pools that are scattered everywhere over the 

 area. Most of these pools are very small and shallow (Fig. 9) ; 

 a few may cover an area of several acres ; some dry up after the 

 close of the rains, while others retain their water up into tne 

 cold season, and a few are permanent. The smaller and shallower 

 and less permanent pools show only the earlier phases of the 

 aquatic stage, for the natural vegetation is always interfered with by 

 man. The constant use of a pool for various domestic purposes 

 destroys most or all of the plants, and irrigation finally removes 

 the water and leaves a mud flat that quickly dries out without being 

 able to support much in the way of plant growth. The green plants 

 in proximity to water are eaten off by grazing animals. Shallow 

 pools are planted with rice during the rains (Fig. 9), and this effectively 

 prevents development of the characteristic wild aquatic vegetation. 

 The small number of native plants that can grow under such 

 conditions are more of the nature of ruderals. Even if a pool is 

 relatively free from human disturbance, the water level is rapidly 

 lowered by evaporation, so that plants that are strictly aquatic 

 during the rains are finally stranded on mud flats to dry out and 

 die, or to survive by means of perennating organs till inundated 

 during the next rainy season (Fig. 8.). 



The aquatic stage may be further divided into :—■ 



Free-floating aquatic stage ; 

 Attached submersed aquatic stage J 

 Attached emersed aquatic stage. 



These stages overlap each other more or less, but they indicate 

 the actual order of normal succession. 



Free-floating aquatic stage. i?his stage is represented mainly by 

 algae, of which there is great variety and considerable abundance. 

 Dhe principal algae are several species of Cyanophyceae, Sinrogyra 

 spp., and Cladophora spp ; others very commonly found, but abund- 

 ant only in very limited areas are Mougeotia spp., Oedogonium spp., 

 Hydrodictyo?if and Vaucheria. The Cyanophyceae are specially 

 abundant in the shallow rainy season pools, though they are rather 



