172 TEXTBOOK OF BOTANY 



into the soil, in a short time each piece may form adventive 

 roots and an adventive bud, and so give rise to a complete 

 new plant. 



194. Vegetative Multiplication. It is plain that the 

 power which the begonia leaf has of forming adventive 

 roots and buds is of great advantage to the plant because it 

 can thus produce new plants under unfavorable conditions. 

 Not many seed plants can develop new plants from a part 

 of a leaf alone ; but there are many cases in which a small 

 part of a plant, by forming adventive roots or adventive 

 roots and buds, can grow into a complete new plant. This 

 fact is taken advantage of by gardeners and foresters, who 

 grow new plants from cuttings more quickly and easily than 

 they could from seeds. Thus a short piece of a young wil- 

 low stem, stuck in the ground, forms adventive roots at its 

 lower end and adventive buds at its upper end and so 

 grows into a tree. 



Many cultivated plants, such as grapes and currants, the 

 flowering " geranium " (which is really a Pelargonium), 

 coleus, and verbena, are propagated by means of cuttings. 

 A cutting usually consists of a short branch bearing one or 

 more leaves or buds. But a new plant of gloxinia, as of 

 begonia, can be obtained from a single leaf or even from a 

 piece of a leaf ; and the bulb-scales of some lilies are used 

 as cuttings. All these are cases of vegetative multiplication, 

 because new plants are produced without waiting for polli- 

 nation, fertilization, and the ripening of a seed. There are 

 other kinds of vegetative multiplication that depend partly 

 or entirely upon the development of adventive roots. One 

 of these is the production of new strawberry plants by means 

 of runners. 



Layering, a method used by gardeners, is not unlike the 

 one that the strawberry uses. In layering, a branch (of a 

 blackberry or raspberry, for example) is bent over to the 

 ground and part of it is covered with soil. Then, from the 



