" 267 



6. Silene acaulis L. Abundant above timber line on the trail 



from Longs Peak Inn to Longs Peak. The petals are a 

 delicate pale pink, varying to whitish. In Schinz and 

 Keller's Flore de la Suisse, they are described as " carnees," 

 which may pass ; but there is no excuse for the descriptions 

 of our American manuals, "purple or purplish" (Britton 

 and Brown ; Nelson) ; "purple, or rarely white " (Coulter) ; 

 "purplish, rarely white" (Synoptical Flora). Our plant 

 has the petals strongly emarginate at end. Britton and 

 Brown say there is a scale at the base of the blade; Nelson 

 says "a small scale at the summit of the claw." As a 

 matter of fact there are two flattened fieshy lobes, con- 

 trasting with the pink of the blade. 



7. Caltha leptosepala f. chionophila {Caltha chionophila Greene). 



The Caltha growing abundantly in damp depressions 

 above timber line is certainly only an alpine form of the 

 species common in the Canadian Zone below. There are 

 two types of high alpine modification, that due to the 

 direct effect of the environment on the individual (as has 

 been actually proved in Europe by transferring plants to 

 lower altitudes) , and that which is inherent in the constitu- 

 tion of the plant. Presumably those plants which are 

 permanently modified, so that they retain their peculiar- 

 ities when grown at lower levels, or refuse altogether to 

 grow below the high alpine zone, have longest occupied 

 alpine situations. No doubt in some cases both types of 

 modification exist in the same plant, and in the case of 

 plants changing by direct response to climatic conditions, 

 those having gametic variations in the same direction 

 would no doubt be favored in the struggle for existence, 

 such variations tending to make the necessary response 

 more certain or more complete. Another case analogous 

 to that of . the Caltha is seen in the common Frasera of the 

 Longs Peak region, which extends to timber line, where 

 it assumes a singular dwarfed appearance, exactly as if 

 the plants had been broken off by some one in the middle, 

 and then stuck in the sand. 



