344 TlMEHRI. 



water as above it, most water plants are adapted to their 

 life in one of three ways : either they float their leaves 

 upon the water, drinking in sufficient air from their 

 broad surfaces to supply the whole plant, as in the water- 

 lilies; or they float bodily upon the water like the pon- 

 tederias, and the little salvinia (S. auriculata) that 

 constantly covers the end of the third lake, in spite of 

 the tons of it that are periodically removed ; and the tiny 

 reddish, imbricated and moss-like azolla (A. caro- 

 liniana) that mantles the surfaces of the trenches 

 in sheltered parts; or, lastly, they have their leaves 

 so finely divided into hair-like segments, on the 

 same principle as a fish's gills, that they are able to 

 live under water, presenting sufficient surface to obtain 

 the supply of air that is as necessary for plants as 

 animals. But if they are flowering plants, the blossoms 

 must be matured above the water, and hence special 

 flowering stems are sent up, sometimes spirally twisted 

 so as to rise and fall with the water, sometimes supported 

 by floating leaves quite unlike the lower leaves in general 

 appearance, though it will be found that the external out- 

 line is the same in both. A familiar example of this is the 

 water-shields or blanket-grass (Cabomba aquatica), far 

 too abundant for planters — and anglers — in the Lamaha 

 and all fresh water trenches, whose little stalked yellow- 

 flowers are supported by a few small floating lily leaves, 

 while those under water are quite fillamentous. The 

 bladder-worts, common up the Lamaha and in the second 

 lake, with spikes of small yellow " snapdragon" flowers, 

 do not need this support, as some of the finely-divided 

 submerged leaves are covered with tiny bladders which 

 keep them floating near the surface. These plants are 



