100 THE SURVIVAL OF THE UNLIKE. [ill 



observation (and upon which I have once reported) in 

 the case of the Chilian strawberry, (Essay XXV.) 

 Within two years this plant, growing in my garden, 

 varied or departed from its wild type so widely as to be 

 indistinguishable from the common garden strawberry, 

 which has been regarded by many botanists to be spe- 

 cifically distinct from the Chilian berry. This remark- 

 able departure, which has enabled me, as I believe, to 

 reconstruct the evolution of the garden strawberry, was 

 one in which no seedling plants were concerned. If all 

 the common garden strawberries owe their origin to a 

 like source — as I cannot doubt — then we have here a 

 most instructive case of sexless evolution, but one in 

 which the subsequent generations reproduce these char- 

 acters of sexless origin by means of seeds. 



This asexual modification is not confined to domesti- 

 cated plants. Any plant which is widely distributed by 

 man by means of cuttings or other vegetative parts may 

 be expected to vary in the same manner, as much ex- 

 periment shows; and if they behave in this way when 

 disseminated by man, they must undergo similar modi- 

 fication when similarly disseminated by nature herself. 

 I need only cite a few instances of habitual asexual or 

 seedless distribution of wild plants to recall to your 

 attention the fact that such means of distribution is 

 common in nature, and that in some cases the dispersion 

 over wide areas is quite as rapid as by means of seeds; 

 and some plants, as various potamogetons, ceratophyl- 

 lums and other aquatics are more productive of detach- 

 able winter buds and other separable vegetalile organs 

 than they are of seeds. The brittle willows drop their 

 twigs when injured by storms of ice or wind, or by 

 animals, and many of these cuttings take root in the 



