H70 PLANTS OF NEW ZEALAND 



by morphological charactei's alone. Each variety will require 

 to be grown from carefully selected seed, and its whole life 

 history known, before its claim to distinctiveness can be 

 l)roperly determined. Until this has been done, no satisfactory 

 list of species can be prepared. 



An enquiry into the causes of this Protean fickleness of 

 form would lead us too far afield. No biological problems 

 however, are more fascinating, or more important, than those 

 presented by tlie variation of individuals within a species ; 

 several of them may therefore be mentioned here. (1) How 

 far is hybridism responsible for variation ? (2) To what 

 extent does change of environment induce variation? (3) Does 

 variation take place by imperceptible gradations, or by small 

 leaps and l>ounds? (4) How far are variations, induced during 

 the life-time of the individual, inherited l)y its descendants ? 

 Tliese (questions liave absorbed the attention of many 

 naturalists for years. Vast quantities of information have 

 lieen collected concerning them. They seem to have been 

 studied, theoretically at least, from every point of view, yet it 

 is questionable whether we have acquired a deeper insight into 

 them than Darwin had, when he wrote his " Origin of 

 Species," now nearl\- fifty years ago. (1) Some affirm the 

 importance of h^'bridization in producing variation, while 

 others deny it. Cl) Change of environment probably induces 

 greater variation than was at one time considered possil)le. 

 Nature is infinitely plastic (c. Discaria, p. 240). (3) The 

 third question has recently been asked anew by the famous 

 botanist, Prof. Hugo de Vries, of Amsterdam ; and he has 

 adduced a considerable amount of experimental evidence, to 

 shew that new species do not arise by imperceptible changes 

 out of the old, but that a large number of similar and 

 concomitant, though perhaps minute, variations are found in 

 certain individuals of the species, and from these individuals a 

 new type arises. Such a discontinuous variation he terms a 

 mutation, and species producing them are said to be mutable. 



