Evidences of Physiological Selection. 87 



their very existence eluded the observation of botanists, 

 until M. Jordan began to search specially for them as 

 the special objects of his scrutiny. Moreover, these 

 varieties of a Linnean species occupy common areas, 

 and there grow in intimate association with one 

 another, or as M. Jordan says, "pile-mile." So far, 

 be it noticed, Jordan was proceeding on exactly the 

 same lines as Nageli ; only he carried his observa- 

 tions over a still wider range of species on the one 

 hand, and into a still minuter search for varieties 

 on the other. But the all-important point for us is, 

 that he further proceeded to test by experiment the 

 physiological relations between these morphological 

 varieties ; and found, in many hundreds of cases, 

 that they not only came true to seed (i. e. are hereditary 

 and not merely climatic), but likewise cross-sterile 

 inter se. For these reasons, M. Jordan, who is 

 opposed to the theory of evolution, regards all such 

 varieties as separately created species ; and the 

 inspiring motive of his prolonged investigations has 

 been a desire to multiply these proofs of creative 

 energy. But it clearly makes no difference, so far 

 as evolutionists are concerned with them, whether 

 all this multitude of sexually isolated forms be de- 

 nominated species or varieties. 



The points which are of importance to evolu- 

 tionists — and of the first order of importance in the 

 present connexion — may be briefly summarized as 

 follows : — 



(i) The research embraces large numbers of species, 

 belonging to very numerous and very varied orders 

 of plants; (3) in the majority of cases — although not 

 all — indigenous species which are of common occur- 



