222 THE STOKY OP THE PLANTS. 



stances. This form may perhaps vary again in 

 other situations, and give rise to individuals 

 better adapted to the second set of circum- 

 stances. But just in proportion as such in- 

 dividuals surpass in adaptation one another will 

 they live down the less adapted. Hence, the 

 intermediate forms will tend to perish, and the 

 world to be filled in the end with groups of 

 plants, each distinct from others, and each 

 relatively fixed and similar within its own 

 limits. 



At all times, and in all places, this process of 

 variation and adaptation is continually going 

 on ; new kinds are being formed, and inter- 

 mediates are dying out between them. For the 

 intermediates are necessarily less adapted than 

 the older form to the old conditions, and than 

 the newer form to the new ones. 



Moreover, when any great point of advantage 

 is once gained by a kind, it tends to go on and 

 be preserved, while variations in other parts 

 continue uninterrupted. Thus, the first com- 

 posite plant (to take a concrete example) gained 

 by the massing of its flowers into a compact 

 head : and it then became a starting-point for 

 fresh developments, each of which maintained 

 the massed flower-head, with its ring of united 

 stamens, while adding to the type some fresh 

 point of its own, which specially adapted it to a 

 particular situation. So, too, the first peaflower 

 gained by the peculiar form of its oddly-shaped 

 corolla, and therefore became the ancestor of 

 many separate kinds, each of which retains the 

 general pea-like type of blossom, while differing 



