152 



Plants and their Ways in South Africa 



five leaves with petioles. 



Before they are ripe they spread 

 open, and the seeds ripen along 

 their edges. In the " Christ- 

 mas Rose," leaves and leaflets 

 take the place of ovaries and 

 ovules. The centre of the 

 flower is a mass of crumpled 

 leaves. In Fig. 150 the centre 

 of the Rose has lengthened 

 and become a leafy branch. 

 As plants come to be propa- 

 gated by other means than 

 seeds, the seeds and seed ves- 

 sels turn their energies toward 

 the work of foliage leaves. 



The frequent similarity be- 

 tween the different whorls sug- 

 gests that in their past history 

 there has been less difference 

 between the whorls than now 

 exists. It may be that perianth 

 and stamens, for example, are modified forms of foliage leaves, 

 or what is more probable, stamens may have given up form- 

 ing pollen in the outer whorls and so have become larger and 

 petal-like owing to the abundance of food material at hand. 



Fig. 150. — The centre of the Rose 

 -■ has grown out into a leafy branch. 



