84 Plants and their Ways in South Africa 



edges toward the noonday sun. The broad surfaces of the 

 lower leaves receive less light. At sunset, when the light is 

 not so strong, the upper leaves receive it on their broad 

 surfaces, and so are prevented from cooling too rapidly. It is 



Fig. 88. — The Black Wattle trees lose all trace of the compound leaves they 

 had as seedlings. 



the position of the upper leaves which gives such a delicate 

 tracery against the sky. 



Sow Mimosa seeds, those of the Karroothorn and Black- 

 wood, or the Port Jackson "Willow." Watch the seeds of 

 both come up " with a loop," bringing their cotyledons with 

 them. On the first leaves note the little bristle-like stipules. 

 Can you see them on both kinds of seedlings ? Are the next 

 leaves the same in each. Watch the seedlings until you find 



