FLORA OF THE INDIAN DESERT. 279 



a habitat of this type seems necessary for it to thrive in this region. It 

 attains its maximum development about 2-3 feet above the surface of 

 the water nearer which young plants and seedhngs only are found, so that 

 zones and islands result. 

 (10) Many smaller pools or tanks were met with, but proved very uninterest- 

 ing. There is generaUy one or two near every village. Rivers containing 

 water there were none. We. crossed a river-bed 2 miles East of Sodakoer 

 (PI. XXX), the vegetation of which hardly differed from the surrounding 

 gravel area. A sandy river-bed at Barmer was totally devoid of 

 vegetation. 

 From the above may be seen that the submerged flora is, as might have been 

 expected, rather poor, and very local. The semi-aquatic flora consists mainly 

 of certain Cyperacece, Lythracece and Elaiinacece, and is often well developed 

 as regards number of individuals. The almost complete absence of Hydro- 

 char itacece is noteworthy. The genus Rotala, too, is absent. There are hardly 

 any aquatic grasses. Desmostachya bipinnata may perhaps be referred here. 

 It frequents irrigated gardens and margins of tanks. 



The occurrence of Naias australis and Naias Welwitschii within our region is 

 veiy interesting, both plants being new to India. 



(To be continued.) 



