TUBEBOnS PABTS 



365 



is so much condensed that it may almost be said 

 to be a tuber. A root- tuber of this kind is 

 shown in Fig. 383, which is a picture of a bean 

 of the Scarlet Runner type. (See, also. Figs. 349, 

 353.) Most beans are fibrous -rooted, and die at 

 the close of one season ; but this bean lives 

 two or more years in warm climates, and carries 

 itself over the inactive seasons by means of its 



Fig. 384. 

 Old potato tuber giving rise to new tubers. 



thickened root. Even in the North, this thick 

 root develops. It would appear that these thick- 

 ened parts develop in plants because of the en- 

 vironments in which the plants grow ; that is, 

 they seem to be adaptations. 



458a. A forcible illustration of the fact that bulbs, conns, 

 tubers, and the like are storehouses of plant-food is suggested by 

 Fig. 384. This represents an old potato tuber (a), from which 

 new tubers have grown, while it was still in the bin. This is a 



