VEGETATIVE PROPAGATION 



213 



be seen, giving biological advantages. For instance, there may be an 

 elongation of the basal internodes, leading not only to vege ative 

 increase, but also to a wide extension of the area occupied. A "runner" 

 is thus formed, and the bud is carried out to a distance from the parent 

 plant. It there roots in the soil without competing with the parent. 

 This is seen in the Strawberry (Fig. 160), the Silver-Weed, the Bugle, 

 and many other creeping herbs. In other cases storage, either in 

 the axis or the leaves of the bud, gives it an additional advantage at 

 the start, especially in plants subjected to seasonal change. Such 

 buds may be produced above ground, as in the bulbils of the Lily or 



FIG. 160. 



Strawberry Plant, bearing axillary buds developed as runners, with long internodes 

 which may branch and root at their distal ends. (Reduced to .) 



Onion ; but more frequently they are buried, as in the Potato (see 

 Fig. 138, p. 185), or Artichoke. Perennation as well as increase in 

 numbers is secured by such measures as these. Sometimes the 

 parent survives, as in Saxifraga granulata, or Scrophularia nodosa ; 

 in other cases it dies, as in the Potato and Jerusalem Artichoke. In 

 the latter cases, since each tuber is borne on an elongated stalk and 

 can grow into a new plant, both spread and increase are secured, as 

 well as perennation. It will be unnecessary to illustrate further the 

 manifold varieties of detail shown in vegetative propagation by means 

 of buds produced in the normal sequence. In nature a very large 

 proportion of individual plants may be traced as having been pro- 

 duced in this way. But it is more common in herbaceous than in 

 woody plants. 



Adventitious buds, that is, buds formed in positions where buds are 

 not normally present, serve the same end, but they are less frequent. 



