114 



BIOLOGY AND HUMAN LIFE 



Differences in form are often related to the conditions under which 

 the plants live. Thus, fleshy roots are often associated with the biennial 

 (two-year) habit. In such plants as beets, carrots, and parsnips the plant's 

 first season is spent in manufacturing food and depositing it in the 

 root. The next year comparatively little foliage is produced, but a stalk 

 bearing flowers uses up substantially all the food that had been accumu- 

 lated. In contrast with this habit of Hfe we find the plants that sprout, 





Fig. 65. Forms of roots 



I, taproot of dandelion; 2, fibrous root of buttercup; 3, bundle (or fascicled) 



root of dahlia; 4, fleshy root of beet 



grow to maturity, and die, all within one season. These ammal plants 

 develop in their short lives rather delicate or fibrous roots, as a rule. 



Trees and woody shrubs, which continue to live year after year, 

 develop massive shoots. Corresponding to this fact we may note that 

 such plants also develop elaborate, strong roots. From this we may see 

 that the structure of the root and its functions are closely related to each 

 other and to the character of the plant. There is a connection (i) be- 

 tween the structure of the root and the size of the plant that it anchors, 

 (2) between the size of a root and the length of its life, and (3) between 

 the size of a root and its food-accumulating or its absorbing activity. 



In many plants the main root continues to grow downward into the 

 soil as long as the plant lives and as long as the tip of the root remains 



