326 



PLANT LIFE. 



upjier to the lower side of the leaf may act as reservoirs 



of water. 



442. 3. Tubers and bulbs. — These forms of the shoot 



in which the parenchyma is 

 alnindant and richly supplied 

 with water may also be 

 counted, in part at least, as an 

 adaptation for water-storage. 

 443. III. Halophytes. — 

 'I'he saltdoving plants are, 

 in most of their characters, 

 strikingly similar to the xero- 

 phytes. This similarity is to 

 be explained probably by the 

 difficulty of securing a suita- 

 ble water supply. They grow 

 near the ocean, upon the 

 shores of salt lakes, by salt 

 s]irings, and in the interior 

 of the great continents in old 

 lake basins in which the salts 

 have accumulated by the 

 rains. A few of the halophytes 

 are trees and shrubs, with 

 leathery lea\'es, but almost all 

 are succulents. In habit they 



Fig 370. — Strip from a vertical section of 

 leaf of Pepei-omiatricJiocar/'ii. .V, fr 



afresh leaf; w, water-storing tissue, com- „,.„ ,-rpnproll v Inn- r,fl,=.n rrpr-i-, 



posed of the multiple epidermis of the aiCgCncrain lOW , OlieU ClCCp- 



upper side; «, chlorophvll-bearing cells; •,,... , 'jl, il.- 1 fl 1 q 



.r. spongy parenchj'ma mfth sparse chloro- "'&' ^''^H linck, UCSn) and 

 plasts and much water. J:l, the same after ^ .-,1 + i 4- i 



four days' transpiration at iS-2o<" c. The morc 01 less translucent leaves 



tissue 7c' is much collapsed, the walls being t 4. ,1 11 1 j 



' ■ • eforc'. and Stems; the cells large and 



landt, " ^ "~ thin-walled, containing com- 



plaited ; ,v also shrunken, hut n as bef( 

 Magnified about 50 diam — After Haber- 



paratively little chlorophyll and abundantly supplied with 

 water, with few and small intercellular spaces and the surface 

 generally smooth. 



