PAPERS PRESENTED AT GENERAL SESSIONS 33 



The outer edges of the rock ledge which are exposed and 

 relatively dry are occupied first by elongated patches of 

 stunted conifers of the species already mentioned. The 

 inner part of the ledge is lower and the scanty soil is 

 watersoaked from melting ice and snow, and in this de- 

 pression a moisture-loviug community develops. The 

 plants here include grasses and sedges, the heathers, and 

 the Rocky Mountain laurel, the globe flower, a buttercup, 

 a cinquefoil, the queencup, a white paint-brush, the 

 meadow rue, the rock-cress, and in protected spots sev- 

 eral delicate ferns. 



When water drips over the face of the ledge, the pro- 

 jections and pockets in the rock face contain hydrophytic 

 mosses and ferns, and such unusual plants as the mist- 

 maiden (Romanzoffia) and the butterwort (Pinguicvla). 

 In especially cold, wet spots a bit of real arctic wet tundra 

 may be found with sphagnum and the arctic heather 

 Cassiope. 



Still another type of community is found occupying the 

 clay-gravel moraines around the melting fronts of the 

 glaciers. (Fig. 4.) Here the conditions are extremely 

 hard for plants on account of the character of the soil, 

 and the exposure and the absence of moisture on these 

 dry, clay ridges. The first plants to appear after the re- 

 treat of the glaciers are stunted and scattered, as they 

 are able to become established only in the most favor- 

 able spots. The first pioneers are usually grasses, with 

 cliickweeds, fleabane, alpine beardtongue, the mosspink, 

 and the alpine poppy. The last mentioned is especially 

 interesting and characteristic as it is a true poppy, but 

 only two or three inches high. It has only a few leaves 

 and one orange-colored flower which is perfectly formed 

 and easily recognized as a poppy. 



On the older moraines these plants form layer clumps 

 and are found closer together. Other less hardy species 

 come in and scanty clumps of stunted conifers begin to 

 appear. Those are the same species that are found on 

 the dry tundra and on the rock ledges. 



