140 



PLANT KELATIONS. 



if necessary, the parts of the leaf or the stem itself twisting 

 to allow the blade to assume this position. The danger of 

 the leaves shading one another is reduced to a minimum by 

 the elongation of internodes, the spiral arrangement, short- 

 ening and changing direction upwards, or lobing. 



This outlines the general nutritive relations, the roots 



FIG. 143a. Germination of the garden bean, showing the arch of the seedling stem 

 above ground, its pull on the seed to extricate the cotyledons and plumule, and 

 the final straightening of the stem and expansion of the young leaves. After 

 ATKINSON. 



and leaves being favorably placed for absorption, and the 

 latter also favorably placed for photosynthesis. 



98. Placing of flowers. The purposes of the flower seem 

 to be served best by exposed positions, and consequently 

 flowers mostly appear at the extremities of stems and 

 branches, a position evidently favorable to pollination and 

 seed dispersal. The flowers thus exposed are very com- 

 monly massed, or, if not, the single flower is apt to be large 

 and conspicuous. The various devices for protecting nec- 

 tar and pollen against too great moisture, and the more 



