322 FRANCIS RAMALEY 



1). If the soil is coarse or has many rocks a mixed inceptive- 

 grassland (6) develops. Here a considerable number of herba- 

 ceous plants appear, the commonest pioneer being Artemisia 

 frigida. Other species of frequent occurrence are Koeleria gra- 

 cilis, Poa crocata, Agropyron richardsonis, Festuca saximontana, 

 Artemisia brittonii, Oreocarya virgata, Achillea lanulosa, Gail- 

 lardia aristata, Opuntia polyacantha, and the shrub Ribes ine- 

 brians. The following quadrat record was made on a gravelly 

 slope, part of a rock-wash fan. The figures indicate the percent- 

 age of ground covered. 



Quadrat 2 



Bare ground and rocks 85 



Artemisia frigida 7 



Artemisia brittonii 3 



Bouteloua gracilis 2 



Pentstemon unilaieralis 1 



Potentilla hippiana 1 



Machaer anther a viscosa 1 



100 



The inceptive grassland here noted is destined to become what 

 the writer has called (6) a derivative grassland, in which there is 

 a closer stand of vegetation with a larger proportion of grasses 

 and fewer species of dicotyledons. At a still later period, if un- 

 disturbed, this should gradually develop into short grass, proba- 

 bly the Bouteloua consociation. The production of short grass is 

 a slow process which depends upon accumulation of humus and 

 further disintegration of soil particles. 



4. Plants of rock ridges 



So far as rock ridges have no sand at all they do not afford 

 material for description in the present paper. Practically all 

 ridges of exposed rock down toward the valley floor have some 

 sandy material. On these ridges shrubs are abundant, especially 

 Ribes inebrians, Sericotheca, and Cercocarpus. This shrub com- 

 munity is represented on both sides of the valley, and is, 

 indeed, common on hillsides of the region. Herbaceous plants 

 are such as occur on rock-wash fans and the coarser parts of 

 sand-gravel slopes. 



