146 THE VEGETATIVE FUNCTIONS OF PLANTS 



found significance to the plant of its ability so to adjust its 

 organs as to bring them into harmony with surrounding 

 influences. If a stem, bent over, could not erect itself, 

 if leaves could not assume positions that secure the 

 most favorable illumination, if stems and leaves were not 

 correlated to each other, most plants would soon be out 

 of harmony with their environment and would sicken and 

 die. Fully one-half the leaves of the motherwort, illus- 

 trated in Fig. 105, would have been deprived of suitable 

 illumination by adjacent plants, had they not possessed 

 this power of adjustment. 



138. Purpose of Part m. — Chapters I to XI have dealt 

 with all parts of the plant except the flower, and all the 

 activities studied have been primarily for the sake of pre- 

 serving the life of the individual plant. Flowers function 

 primarily for the race to which the individual plant 

 belongs; but they can be really understood only after a 

 thorough study of the life histories of some of the lower, 

 non-flowering plants. The study of life histories will be 

 taken up in Part III. 



