THE LEAF 



211 



than if they were green throughout. (A dark coat feels warmer 

 than a bright one.) Similarly, the leaves of the Lotus plant 

 are coloured} dark-purple on their under side. 



Many plants, like the Bean and almost all Leguminosse, have 

 the curious habit of folding their leaves at night. This, again, 

 is an ingenious 

 device to pre- 

 vent dew from 

 covering them 

 and thus chok- 

 ing the pores, 

 so that the ac- 

 tion of trans- 

 piration may 

 not suffer (see 

 page 34). 



Other plants, 

 like the Opium 

 Poppy and Co- 

 locasia, possess 

 a bloomy coat 

 of a ivaxy sub- 

 stance on their 

 leaves so that 

 they are not 

 wetted, and the 

 process of eva- 

 poration may 

 not be inter- 

 rupted. 



Most leaves 

 taper into a 

 point instead 

 of having a 



blunt end. This enables them to become dry soon after the 

 rain ceases, as the raindrops fall easily to the ground from such 

 tapers. 



Fig. 195.- 



Tlie Silk Cotton tree in the dry season: 

 but fruit-bearinff. 



leafless 



14* 



