[Chap. XXXV 



VEGETATIVE MULTIPLICATION 



405 



Vegetative multiplication may also occur at the nodes of leafy prostrate 

 stems, and at the nodes of elongated stems of such plants as raspberry, 

 grape, and honeysuckle, which bend over and come in contact with moist 

 soil. In horticultural practice the stems of such plants are bent over and 

 some of the nodes or whole stem tips are covered with soil: a procedure 

 called layering (Fig. 178). The terminal buds of the buried stem grow 

 upward and adventitious roots grow from the oldest buried nodes. The 

 rooted branches may then be severed from the parent plant and trans- 

 planted. 



In bog forests propagation of trees by layering occurs naturallv when 

 the lower branches of spruce and arbor vitae lie on the ground or are 

 pressed down by snow. This method of propagation may be more fre- 

 quent among bog plants than propagation bv seeds. Lavering by leaf 

 tips occurs in a few species of plants, such as the walking fern. 



Rhizomes. Many perennial grasses, fems, mints, and a host of other 

 plants have rhizomes from the nodes of which roots and aerial shoots 

 develop ( Fig. 179 ) . The rhizomes may elongate each vear bv the growth 

 of temiinal buds. When the older parts of these rhizomes die, groups of 

 individuals of the clone become separated and are new centers of dis- 

 persal by growth of rhizomes. 



As a result of this method of propagation, certain perennial grasses 

 and other perennial herbs become the dominant plants of the vegetation 

 of lawns and meadows, and of the natural prairies and plains in various 



Fig. ISO. Erosion stopped by the kudzu vine. The ditch is now being filled by the 

 accumulation of silt. Photo horn the U. S. Soil Conservation Service. 



