218 Science of Plant Life 



corms, and tubers bring about vegetative propagation in a 



similar way. 



Plants may multiply from the aerial vegetative parts also. 



The stems of the raspberry com- 

 monly bend over, and where they 

 touch the ground they form buds 

 from which adventitious roots and 

 new upright stems develop. A 

 grapevine will take root where a 

 node comes in contact with the 

 soil. In the walking fern (page 



FIG. 134. Bryophyllum leaf, with 283) the tips of the leaves develop 

 young plants starting from the - 



notches in the margin. buds, roots, and new plants when 



in contact with the soil. The 



strawberry is an example of certain plants, including many 

 grasses, which have horizontal branches (runners) on the soil 

 surface that take root at intervals and produce new plants. 

 In Bryophyllum, a weed in cultivated fields of the West 

 Indies, the leaves when they fall to the ground develop new 

 plants from the notches in their margins (Fig. 134). 



These illustrations, which might be multiplied, show the im- 

 portance of vegetative propagation in the increase and spread 

 of plants. Among wild plants it is entirely possible that vege- 

 tative multiplication is as effective in spreading the plants as 

 is reproduction by seeds. By the former method the young 

 plant is able to start more vigorously than a seedling, because 

 it is able to draw water and food materials from the parent 

 plant until its own root and leaf systems are well developed. 



Vegetative propagation of cultivated plants. In agriculture 

 and horticulture, vegetative multiplication is relied upon for 

 starting many cultivated plants. Potatoes, mint, horse- 

 radish, sugar cane, sweet potatoes, and certain varieties of 



