No. 529] 



ORGANIC RESPONSE 



11 



tural features of the individual, may be repeated or car- 

 ried over two or three generations, in a habitat where 

 the specific causal combinations are lacking. This is the 

 available total of knowledge furnished us by economic 

 operations, and by the introduction operations of botan- 

 ical gardens and plantations. 



In contrast with these the fortunate experience of Zed- 

 erbauer with Capsclhi lias yielded some conclusions of 

 exceptional importance. A genotype of Capsella Bursa- 

 pastoris resembling tara.ricafoliif m was found on the 

 lower plains of Asia Minor, and displayed the well- 

 known characters of this form, including broad leaves, 

 whitish flowers, and stems ;>() 40 cm. high. A highway 

 leads from these regions to a plateau at an elevation of 

 2,000 to 2,400 meters. The conditions of distribution are 

 such as to indicate that the plant lias been carried up 

 this thoroughfare by man, and in this elevated habitat 

 it has taken on certain alpine characters, including elon- 

 gated roots, xerophytic leaves, stems 2-5 cm. high, red- 

 dish flowers, with a noticeable increase of the hairiness 

 of the entire plant. That the distributional history has 

 been correctly apprehended seems entirely confirmed by 

 the fact that when seeds are taken from the lowlands the 

 alpine characters enumerated are displayed at once as a 

 direct somatic response. When seeds are taken from 

 plants on the elevated plateau where their ancestors may 

 have been for many years or many centuries ( perhaps as 

 long as 2,000 years) and sowed at Vienna and in other cul- 

 tures carried through four generations the leaves lose 

 their xerophytic form and structure, but the other charac- 

 ters are retained within the limits of variability. The 

 stems show an increase in average length of 1 or 2 cm., 

 the roots change as much, but the reproductive brandies 

 and Moral organs retain their alpine characters. The 

 slight modifications undergone by these features were 

 seen to reach a maximum and to decrease in the latest 

 generations cultivated. The structural changes and im- 

 plied functional accommodations are indubitably direct 



