MOUNTAIN OR ALPINE VEGETATION 



487 



The gradual diminution of the height of the trees on ascend- 

 ing a mountain is well shown in Fig. 3 7 1. 1 The treeless charac- 

 ter of the mountain summit is also plain. 



Kecent experiments have shown that many ordinary plants 

 promptly take on alpine characteristics when they are transferred 

 to moderate heights on mountains. For instance, a rather com- 

 monly cultivated sunflower, 2 when planted at a height of about 

 sixty-five h u n d r e d 

 feet, i n s te a d of 

 having a tall, leafy 

 stem, produces a 

 rosette of very hairy 



V f 



leaves lying close to 

 the ground, thus be- 

 coming almost un- 

 recognizable as a 

 sunflower. The 

 change is e v e n 

 greater than that 

 shown in the rock 

 rose (Fig. 372) culti- 

 vated by the same 



V 



experimenter. The 



peculiarities pf alpine 



plants appear to be FIG. 372. Two plants of rock rose (Helianthemum] 



due mainly to the in- A, low ground form; />', alpine form. Both drawn 



t e n s e 1 i g h t w h i c h to the same scale 



they receive during the daytime, 3 to the strongly drying char- 

 acter of the air in which they grow (due partly to its rarefaction), 

 and to the low temperature which they must endure at night. 



1 Part of the diminution is only apparent, the effect of distance, --but 

 the growth at the highest levels is often less than waist high. 



2 Helianthus tuberosus, the so-called Jerusalem artichoke. 



3 The experiments of Professor Frederic E. Clements on Pikes Peak, 

 however, seem to show that light is not a principal factor in the production 

 of alpine characteristics in plants. 



