species ill Nature. 175 



tures where groups of many individuals of the different 

 types grow close together. The characters are sometimes 

 of such a kind that they are easily recognizable even on 

 dried material; but they very often disappear entirely 

 or partly when the plants are pressed. 



The constancy and thus the distinctness of the local 

 species can only be proved by cultivating the plants from 

 seed.-^ Experiments of this kind have been carried out 

 on a large scale by Koch and Fries and other well- 

 known systematists but especially by Jordan and his 

 pupils. In many cases these experiments have been re- 

 peated and always with the same result. Thuret and 

 Bonnet grew 14 of Jordan^s species of Draba verna, 

 4-6 species of Papaver dnhiinn, for about 7 years and 

 convinced themselves of the constancy of these forms.^ 



This statement is supported by the high authority of 

 De Bary, who satisfied himself as to the constancy and 

 systematic distinctness of the numerous subspecies of 

 Draba verna,^ as the result of his well-known researches, 

 which were continued and published after his death by 

 F. Rosen. This splendid work has received full recog- 

 nition, but it has not had the effect which De Bary evi- 

 dently hoped it would have on his contemporaries, of 

 directing research more generally into these channels. 



A similar state of affairs obtains in zoology. Every 

 ?oologist knows, as Bateson remarks,^ that in the case 

 which we owe to the exhaustive and important researches of Ericks- 



SON. 



^ Conclusions based on comparative study only should never he 

 regarded as proofs in this field. See the Flora Europae of Gandoger. 



^J. CosTANTiN, Accomodation dcs plantcs, Bull, scientif. publie 

 par GiARD, Vol. XXXI, p. 507. 



^ F. Rosen, Systematische und biologische Beohachtungen iiber 

 Erophila verna, Bot. Zeitung, 1889, No. 35. 



* W. Bateson, On Progress in the Study of Variation, Science 

 Progress, Vols. I and II, 1897-98. Vol. II, p. i. 



