204 THE STORY OF THE PLANTS. 



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

 variation and adaptation is continually going on ; 

 new kinds are being formed, and intermediatef 

 are dying out between them. For the interme 

 diates 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 con 

 tinue uninterrupted. Thus, the first composite 

 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 develop- 

 ments, each of which maintained the massed flow 

 er-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 situ- 

 ation. 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 in other respects 

 as widely from its neighbours as gorse and clo- 

 ver, peas and laburnum, broom and vetches, scar- 

 let-runners and lupines. A group of kinds, so de 

 rived from a common progenitor, but preserving 

 throughout one or more of that progenitor's pe- 

 culiarities, while differing much in other respects 

 among themselves, is called a family. Thus we 

 speak of the family of the peaflowers, the family 

 of the roses, the family of the lilies, the family of 

 the orchids. Each family may include several 

 minor groups, known as genera (in the singular, a 

 genus) ; and each such genus may further include 

 several distinct kinds or species. 



