^6 Plants and their Ways in South Africa 



cloth." We have seen what a great amount of water, which is 

 required to bring up the dissolved mineral matter, must pass 

 off in the form of vapour. Vapour cannot pass off if the leaves 

 are water soaked. Place a silver leaf in water and notice how 



im&sa^.'SsS'i^i. w- feA^v'si' "^T^TZ ^.~>^ -• ' «-,. 



''^"^«aJ®^'' 



Fig. 77. — Vegetation in the Karroo where there are long droughts. The 

 soil is alkaline. 



the silvery sheen is brightened. The thick coat of hairs retains 

 a layer of air which the rain cannot replace. It is because of 

 this that vapour can pass off without interruption. A bamboo 



leaf under water glistens on the 

 lower surface quite as brilliantly, 

 but the upper surface comes out 

 wet. The stomata are on the under 

 side only of these leaves. It does 

 not matter if the upper side is wet. 

 On the lower side small rods of 

 wax take the place of the hairs of 

 the silver leaf. 



The sugar-bush has another 



cunningly devised method of pro- 



The cells bordering the stomata over- 



FiG. 78. — Section of sugar - bush 

 leaf through a stoma : a, the 

 guard-cell ; b, projecting dome ; 

 c, thick cuticle. 



tectmg Its stomata 



arch, forming a little hut with an opening at the top, so small 



