PLANT REPRODUCTION 



103 



partly covered with soil, and grow. Some few plants, such, as the 

 Bryophyllumfh, produce buds and new plants from the margins 

 of the leaves, but this method is comparatively rare. 



Many of the principles of plant propagation as practiced by 

 the horticulturists are baaed on the above facts concerning plant 



Fig. 75. — Self-pruned twigs of the poplar showing the cleavage planes. 



gi'owth. Many herbaceous plants, such as geraniums, begonias 

 and carnations, are grown almost entirely from cuttings. 



Grafting. — Thisi is an art which is very generally practiced 

 by the hoirticulturists in the growing of fruit trees and many 

 other plants. It consists in uniting the p-arts of two growing 

 plants, known as the stock and the scion, in such a manner that 

 the tissues will unite into a single plant. The stock is the root, 

 or root and part of the stem, and should be a strong, vigorous 

 plant ; the scion is a twig or bud from a plant which it is desired 

 to perpetuate and therefore produces desirable flowers or fruit. 



