﻿49° BOTANICAL GAZETTE [june 



Such shrubs as show any considerable length of stem commonly 

 lie prostrate, thus giving evidence of the crushing effect of the 

 masses of snow that cover the lower meadows during 9 or 10 

 months of each year. Of these Rhododendron albiflorum and 

 Vaccinium membranaceum are most frequently met with on the 

 lower slopes, especially on those threaded by rivulets originating 

 in snow banks higher up. Farther up the slopes, and reaching 

 quite to the alpine deserts, dwarf willows, Arctostaphylos Uva-ursi, 

 Cassiope Mertensiana, Empetrum nigrum, Bryanthus glanduliflorus , 



B. empetriformis, Gaultheria myrsinites, Kalmia glauca, Dryas 

 octopetala, and occasionally D. Drummondii are the dwarfed 

 shrubs. These sometimes form small patches in the grassland; 

 sometimes they form extensive carpets covering many square 

 meters. Mats of Cassiope or of Bryanthus or Dryas form dry 

 hummocks in comparatively wet meadows. As these mats enlarge 

 year by year, the plants at the center die, thus bringing about the 

 formation of rings of shrubby growth surrounding dead and 

 blackened centers. This seems to bear out Schroeter's state- 

 ment: 5 "Das dichte Heidekrautgestriipp erzeugt einen ganz 

 eigenartigen, schwarzen, nahrstoffsarmen Humus, der eine Menge 

 von Arten ausschliesst." 



Moisture and the presence or absence of snow covering during 

 the short growing season seem to be the principal factors determin- 

 ing the nature of the herbaceous vegetation of the alpine meadows. 

 On very wet slopes and depressions, where the ground is continually 

 soaked by water from the melting of the snow fields higher up, 

 there are commonly either nearly pure stands or mixed associations 

 of the following: Ranunculus alpinus, Trollius albiflorus, Caltha 

 Macounii, Lutkea pectinata, Valeriana Scouleri, and Erythronium 

 grandiflorum. With these are associated, in lesser quantities, 

 Mitella nuda, Petasites frigida, Oxyria digyna, Rumex crispus, 

 R. acetosella, Parnassia parviflora, P. fimbriata, Saxifraga rivularis, 

 S. Lyallii, S. nivalis, Thalictrum occidentals Epilobium angusti- 

 folium; numerous sedges and grasses, among them Car ex invisa, 



C. nigricans, C. livida, Poa arctica, and P. alpina. The stretches of 

 Erythronium and of Trollius. varied by very intruding plants of 



« Schroeter, C, Das Pflanzenleben der Alpen. 



