43 2 RELATION TO ENVIRONMENT. 



cult to see how the helicoid, or scorpioid, cymes are of any 

 advantage to the plant over a true cyme. The inflorescence of 

 the plant being determinate, if the flowering is to be extended 

 over a considerable period a peculiar form would necessarily 

 result. In the helicoid cyme continued branching takes place 

 on one side, and the result in the forget-me-not is a continued 

 inflorescence in its effect like that of a continued raceme (com- 

 pare shepherd' s-purse). But we should not expect that all 

 of the complex and specialized structures from simple and gen- 

 eralized ones are beneficial to the plant. In many plants we 

 recognize evolution in the direction of advantageous structures. 

 But since the plant cannot consciously evolve these structures, 

 we must also recognize that there may be phases of retrogression 

 in which the structures evolved are not so beneficial to the plant 

 as the more simple and generalized ones of its ancestors. Varia- 

 tion and change do not result in advancing the plant or plant 

 structures merely along the lines which will be beneficial. The 

 tendency is in all directions. The result in general may be dia- 

 gramed by a tree with divergent and wide-reaching branches. 

 Some die out; others remain subordinate or dormant; while 

 still others droop downward, showing a retrogression. But in 

 this backward evolution they do not return to the condition of 

 their ancestors, nor is the same course retraced. A new down- 

 ward course is followed just as the downward-growing branch 

 follows a course of its own, and does not return in the trunk. 



