Double Adaptations 441 



procumbent, the flowers being large and of a 

 deep yellow. At Cadeac and at Paris the whole 

 plant changed at once, the shoots becoming 

 elongated and loose, with broad and flattened, 

 rather smooth leaves and numerous pale-hued 

 flowers. The anatomical structure exhibited cor- 

 responding differences, the intercellular spaces 

 being small in the alpine plant and large in the 

 one grown in the lowlands, the wood-tissues 

 strong in the first and weak in the second case. 



The milfoil (Achillea Mille folium) served 

 as a second example, and the experiments were 

 carried on in the same localities. The long and 

 thick rootstocks of the alpine plant bearing 

 short stems only with a few dense corymbs 

 contrasted markedly with the slender stems, 

 loose foliage and rich groups of flowerheads of 

 the lowland plant. The same differences in in- 

 ner and outer structures were observed in nu- 

 merous instances, showing that the alpine type 

 in these cases is dependent on the climate, and 

 that the capacity for assuming the antagonistic 

 characters is present in every individual of the 

 species. The external conditions decide which 

 of them becomes active and which remains in- 

 active, and the case seems to be exactly paral- 

 lel to that of the water-persicaria. 



In the experiments of Bonnier the influence 

 of the soil was, as a rule, excluded by trans- 



