156 



GENERAL BOTANY 



by mechanical injury or by 

 decay, leaving two separated 

 plants instead of one. Such 

 vegetative methods result in 

 clusters of new plants, often 

 seen in the case of dandelions 

 in lawns and gardens. 



One of the most familiar ex- 

 amples of vegetative reproduc- 

 tion by highly modified stems 

 is the tuber of the common 

 potato (Fig. 78). The potato, 

 as the figure shows, is merely a 

 greatly swollen portion of an 

 underground stem, in which 

 the buds, or eyes, retain the 

 power of growth into new plants 

 when placed under proper con- 

 ditions. Since each eye can 

 form a new plant if it remains 

 in contact with some of the 

 stored food within the cells of 



the tuber, it is readily seen that a very rapid multiplication may 



result by this means. In cultivation it is the practice to cut the 



tuber into several pieces, 



each bearing one or more 



buds, thereby increasing 



the output of plants from 1 1 Root 



single tubers. In the bulb 



(Fig. 79) and the corm 



(Fig. 80) the stem is 



greatly shortened and the 



leaves are highly modified 



scales. Bulbs and corm 



thus resemble ordinary 



buds in which the stem axis 



ceases to grow in length p IG . 73. Production of tubers in the potato 



FIG. 77. Multiple stems in plantain 



