^s^o. 484] CLOSELY RELATED SPECIES 



223 



which he is obliged to assign to these forms; without, of course, 

 using the terms of the Mutation Theory, which he partially antici- 

 pates by several years. "The Erophila [Draba] species owe 

 their existence to the free variation of their forefathers. This 

 consists not in a mere heightening or further development of single 

 characters, but variation fashions new characters and combines 

 old characters in new ways. Therefore the forms which arise 

 from species do not intergrade." 



He says that, while Selection plays no part in the origin of these 

 forms it operates upon them after they appear. And of the laws 

 which must control this sort of variation he speaks as follows: 

 "Variation is not blind, vaguely working in all directions, but is 

 obviously determined by laws unknown to us: for we are obliged 

 to assume that the same or similar combinations of next-related 

 forms have arisen in different places. But what can these laws 

 be?" It is most interesting and significant that Rosen is led to 

 these de Vriesian conclusions through florisfic and geographic 

 studies. 



The following excerpt from A. Jordan (73, p. 4) has so direct 

 a bearing upon our argument that I give it entire : " Ayant observe 

 dans leurs stations diverses, pendant plus de trente ann^es, une 

 foule de veg^taux de toutes les families et de toutes les categories, 

 des plantes annuelles ou vivaces, bulbeuses ou aquatiques, des 

 arbres ou des arbustes, j'ai pu constater presque partout que 

 lorsqu'un type linneen, vraiment indigene dans une contree, y 

 dtait commun a ce point qu'on pouvait le citer parmi les plantes 

 caractdristiques de la vegetation d'une certaine etendue du terri- 

 toire, ce type y etait presque toujours represente par des formes 

 diverses, plus ou moins nombreuses, croissant en sociSte et pele- 

 melc [ital. mine]. L'observateur superficiel, qui parcourt le terrain, 

 n'est frappe que des ressemblances de ces diverses formes; il 

 n'aper9oit pas leurs differences, ou, n'y attachant aucune impor- 

 tance, il ne s'arr^te pas a les consid^rer attentivement; il croit 

 n'avoir affaire qu'^ un type unique, susceptible de quelques 

 modifications accidentelles et sans valeur. Tandis que celui 

 qui observe avec attention pent aisement se convaincre, sur les 

 lieux, que ces modifications apparentes se retrouvent sur des 

 individus divers, tous parfaitement semblables entre eux. Si, 



