VI.] PROGRESSION IS GRADUAL. 177 



cultivation and cultivated plants as agent and objects 

 which are similarly expanding through the passing 

 of time. There cannot be one philosophy for untamed 

 nature and another for tamed nature. 



But you want some summary means of producing 

 new varieties. You want varieties quickly, and they 

 must be distinct. You turn at once to hybridization. 

 You must remember, however, that hybrid varieties 

 have not been wrought out with the hammer and the 

 anvil of adaptation, but have been cast forthwith from 

 a mould of conventional pattern. Hybridization is nor- 

 mally rare. Nature rarely does things by jumps. There 

 is no proof that she ever made a species or a potent 

 form in this way. But she mildly crosses one species 

 with itself, and out of the slightly variable offspring 

 selects those which are best adapted to the place in 

 which they live, and uses them for the subjects of 

 another congenial cross ; and so the family marches 

 on from generation to generation, each step slow but 

 each one sure. If man makes hybrids, he must gen- 

 erally propagate them by buds, or parts other than 

 seeds, to keep them "true," as in the few hybrid 

 grapes, pears, raspberries and blackberries which we 

 have and in various hybrid ornamental plants ; and 

 as a rule these varieties are less adapted to wide ranges 

 of conditions than are those which spring from legiti- 

 mate sources. Change of seed and crossing between 

 the different stocks are far more important agencies 

 of the evolution of our field crops than hybridization 

 or other forced effects. 



Nature, then, gives the variations. Man is ordina- 

 rily only a secondary agent in their production. We 

 shall find that in many of those groups of plants in 



12 SUR. 



