HUTCHINSON'S POPULAR BOTANY 



FIG. 48. SEEDLING OAK. 



The store of nutriment packed into the acorn is 

 sufficient to maintain the seedling until it has formed a 

 stem and leaves and the beginnings of its root system. 



the lower one-celled forms a compari- 

 son, however, which must be taken 

 with some reservation. The comparison 

 is not less suggestive to the physiolo- 

 gist than to the morphologist. In the 

 lower one-celled forms all -the vital 

 functions are performed by a single cell. 

 In the multicellular forms, on the other 

 hand, these functions are not equally 

 performed by all the cells, but are in 

 varying degree distributed among them, 

 the cells thus falling into plrysiological 

 groups or tissues, each of which is es- 

 pecially devoted to the performance of 

 a specific function." (Of this we shall 

 speak more fully in succeeding chap- 

 ters.) " Thus arises the physiological 

 ' division of labour ' through which 

 alone the highest development of vital 

 activity becomes possible, and thus the 

 cell becomes a unit, not merely of struc- 

 ture, but also of function. Each bodily 

 function, and even the life of the 

 organism as a whole, may thus in one 

 sense be regarded as a resultant arising 

 through the integration of a vast num- 

 ber of cell activities ; and it cannot be 

 adequately investigated without the 

 study of the individual cell activities 

 that lie at its root." 



On looking at a young seedling 

 say of an Oak (fig. 48) or Chestnut- 

 tree the question naturally arises, How 

 is it that so small and tender a plant, 

 which may be bent with the finger, 

 is capable of growing into a mighty 

 forest-tree that shall defy the winter 

 storms of centuries ? If the cells of 

 which the j^oung plant is formed were, 

 in their beginnings, only so many little 

 specks of protoplasm, each surrounded 

 by a thin diaphanous wall of cellulose, 

 which the shake of a hand would cause 

 to dissolve away, by what mysterious 



