180 



I'LAXT STUDIES 



out of water submerged plants wliicli seem to be upright, 

 with all their parts properly spread out. When removed they 

 collapse, not being aljle to support themselves in any way. 

 (5) Development of air cavities. — The presence of air in 

 the Ijodies of water plants is necessary for two reasons: (1), 



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f"/- 



\u — 





.ii 





4 i 





Vi 





Fig. nil. Bladderwort, sbuwiug the nLimerou:^ Ijladders whicli ll(jat the ])lant, the 

 finely divided water leaves, and the erect flowering stems. The bladders are also 

 effective " insect traps," Utncvlaria being one of the " carnivorous plants.'' 

 — After Kerner. 



to aertite tlio plant ; (2), to increase its buoyancy. Inmost 

 complex water plants there must be some arrangement for 

 tlie distrilnition of air containing oxvgcn. This usualh' 

 takes the form of air cliamljcrs and jiassagoways in the 

 liody of the plant (see Figs. 87, 88, 80, 1)0). Of course 

 Bucli air chamljers increase the hunyancy of the liody. 

 Sometimes, liowevcr, a sjiccial buDvani'v is provided I'm' 

 by the development of reguhir lloats, which are bladder- 



