44 Plants and their Ways in South Ajrica 



horizontal branches of Carissa ferox, E.M. show this. They are 

 arranged in pairs. The leaves which are exposed to the light are 

 large, while the alternate pairs at right angles to these are not 

 so well placed to receive the light and, perhaps for this reason, or 

 because the pair on either side have developed at their expense, 

 they remain much smaller. Other examples of the same nature 

 may be seen in the study of flowers, where one whorl is often 

 developed at the expense of another. In the ray flowers of 

 Compositae, where the corolla is conspicuous, the stamens are 

 wanting ; this may give a chance for the ovaries to develop or 

 they too may be sacrificed, as in the sunflower. While in the 

 less conspicuous disk flowers where the stamens develop, the 

 ovaries may fail to form fruit as in Othonna, Osteospermum, and 

 Eriocephalus. 



On page 17 a correlation was found to exist between the 

 development of root hairs and the supply of moisture. 



