Double Adaptations 439 



tween these two alternatives, many writers 

 have tried to decide, by transplanting their 

 specimens, after some time in the garden, into 

 arid or sandy soil, in order to see whether they 

 would resume their alpine character. 



Among the systematists who tested plants in 

 this way, Nageli especially directed his atten- 

 tion to the hawkweeds or Hieracium. On 

 the Swiss Alps they are very small and ex- 

 hibit all the characters of the pure alpine type. 

 Thousands of single plants were cultivated by 

 him in the botanical garden of Munich, partly 

 from seed and partly from introduced root- 

 stocks. Here they at once assumed the 

 tall stature of lowland forms. The indentical 

 individual, which formerly bore small rosettes 

 of basal leaves, with short and unbranched 

 flower-stalks, became richly leaved and often 

 produced quite a profusion of flower-heads on 

 branched stems. If then they were trans- 

 planted to arid sand, though remaining in the 

 same garden and also under the same climatic 

 conditions they resumed their alpine charac- 

 ters. This proved nutrition to be the cause 

 of the change and not the climate. 



The latest and most exact researches on this 

 subject are due to Bonnier, who has gone into 

 all the details of the morphological as well as 

 of the physiological side of the problem. 



