168 THE SURVIVAL OF THE UNLIKE. [vi. 



elements, according to Weisniann's view, that it becomes 

 hereditary. It is no doubt true that the priinai> reason 

 for the existence of sex in animals and- plants is that 

 offspring may be constantly re -invigorated and diversi- 

 fied by the union of two unlike individuals; for if noth- 

 ing were to be desired but simple reproduction, the 

 ancestral method of cell -division and bud -propagation 

 would no doubt have been perpetuated, inasmuch as it 

 is a much more economical method than sex -repro- 

 duction. But whilst philosophers accept Weismann's 

 assumption that sex has come about for the purpose of 

 imparting variability to the offspring, the contrary prop- 

 osition, — that all permanent variation is a result of 

 sexual union — is obviously iiiitnic. It is disproved in 

 many ways, but chiefly by the facts that hosts of fungi 

 are permanently asexual; and that every branch of a 

 tree is really an individual, and is unlike all other 

 branches, the same as any distinct plant is unlike all 

 other plants, — a fact familiar to all careful nurserymen, 

 for they know that the value of a fruit tree depends 

 very much upon what part of the original or cion- 

 bearing tree the cion was borne. (Compare Essay III.) 

 These three facts, then, I wish to iini»itss 111)011 you : 

 First, that every plant is unlike every other plant; 

 second, that every branch is unlike every other branch 

 in some character of growth, shape, character of flowers 

 or fruit, or the like; and third, that many of these vari- 

 ations may and do originate because of the conditions in 

 which the plants grow. Here, then, is the fundamental 

 source, so far as the horticulturist is foncerncd, of tlie 

 evolution of new varieties, and even ot the possibility 

 of cultivating plants at all. The expert cultivator imisl 

 come to look at every plant, and even at every part of 



