90 



INTRODUCTION TO BOTANY 



though it is better not to cut the potato into too small pieces 

 for propagation, or the plants will grow slowly at first. 



Why are potatoes almost always grown from the tuber 

 rather than from seed ? Why are plants of the Lily family 



grown from bulbs ? 



86. Stolons, runners, and cuttings. 

 Some plants, as the black raspberry 

 (fig. 72), are naturally propagated 

 by recurved branches which root 

 wherev.er they touch the earth. 

 Such rooting branches are called 

 stolons. An artificial modification 

 of this process (called layering}, 

 sometimes made use of in growing 

 apples, pears, plums, and quinces, 

 consists in bending down branches 

 and covering portions of them with 

 earth until they become well rooted. 

 Runners, like those of the straw- 

 berry, are very slender, nearly leafless, 

 stolons. 



Cuttings are twigs or branches 

 cut off, set in the earth, and kept 

 there until they become well rooted 

 (fig. 73). Numerous woody plants, 

 such as willows, grapevines, currant 

 bushes, gooseberry bushes, and gera- 

 niums, and some herbaceous plants, 

 such as the hopvine and the Wan- 

 dering Jew, are usually grown from 

 cuttings. Many others, such as the 

 French marigold and the garden portulaca, not usually thus 

 grown, may be readily propagated by cuttings. In the case of 

 woody plants the cutting should be taken from well-matured 

 twigs of the previous season. To avoid wilting, leafy cuttings 

 are often kept covered for a time with a tumbler or bell glass. 



FIG. 73. A willow cutting 



The roots are a little more than two 

 months old. Somewhat reduced 



