NATURE OF PLANTS 



95 



develop buds and roots from their nodes and so establish new 

 plants. 



48. The Condensed Type of Stems. — In many cases we find 

 that the food is localized in special regions of the rhizome which 

 consequently become enlarged and rather fleshy. Such modified 

 parts of a rhizome are called tubers, e. g., the potato and Jerusalem 



Fig. 70. Fig. 71. 



Fig. 70. Rhizome of Solomon's seal with aerial shoot just emerging 

 from the ground. The seal-like scars mark the successive shoots pro- 

 duced during the past three years. 



Fig. 71. Formation of tubers: A, old potato or tuber with two shoots 

 reaching up into the air and from the base of these shoots, rhizomes have 

 been formed that are developing new tubers. B, mature tuber with spirally 

 arranged buds, the so-called " eyes " of the potato. 



artichoke (Fig. 71). The potato is formed by the storage of 

 foods in certain parts of the rather small rhizomes that branch out 

 from the stem of the plant. The " eyes " are the buds that de- 

 velop at each node of the rhizome and each is capable of forming 

 a shoot, although but a few of them so function, as is the case 

 in an ordinary branch of a tree. By passing a thread around a 

 potato so that it touches each successive bud you will see that 

 there is the same arrangement of the buds as appears in the 

 leafy stem. 



A great variety of plants develop only very short stems that 

 are more or less buried in the ground. This type of stem modi- 

 fication is of great advantage in many ways. The vital parts 

 of such plants are only slightly exposed and consequently suffer 

 little from grazing animals or other sources of injury, as in 



