82 A Study of the Vegetation of 



Erythronium grandiflorum Leptotaenia multifida 



Fragaria bracteata Lupinus laxiflorus 



Fragaria platypetala Lupinus ornatus 



Frasera fastigiata Moehringia macro phylla 



Galium spp. Pentstemon pinetorum 



Geranium viscosissimum Potentilla blaschkeana 



Helianthella douglasii Pteridium aquilinum pubescens 



Hieracium albiflorum Sedum douglasii 

 June aides campestre 



As the pine forest becomes more closed the shrubs tend to dis- 

 appear, and usually considerable Douglas fir and tamarack are to 

 be found. The transition from pine to the pine-Douglas mictium 

 or Douglas-Lamr mictium takes place in this manner. Not only 

 has the closed pine forest established more congenial conditions 

 for tree seedlings, but it has made its own reproduction difficult 

 if not impossible by a cutting down of the light intensity. In 

 order for yellow pine to thrive, the sun must strike the seedling 

 the greater part of the day. Small openings in forests made by 

 the removal of a few trees by windfall or natural death do not 

 furnish sufficient light. However, the slightly more tolerant 

 Douglas fir and tamarack can not only grow here, but actually 

 shade out competing pine species. Thus the physiognomy of the 

 forest may gradually change from pine to Douglas fir or to Doug- 

 las fir and tamarack with all intermediate combinations in mic- 

 tium. Consequently, mixed forests of pine and Douglas fir into 

 which Larix is invading are common. The shrubby and herbace- 

 ous flora, of course, is intermediate between that already given 

 and that of the more mesophytic Pseudotsuga-Larix mictium to 

 be described. 



The Pseudotsuga Consocies. Well developed communities of 

 Douglas fir occupy the upper exposed slopes in the mountains. 

 Frequently the stand is 90 per cent, or more pure Douglas fir but 

 lower down the slopes it is almost invariably mixed with Larix 

 and white fir, to which, along the ravines, it may almost entirely 

 give way. Likewise, in more open places it is accompanied by 

 yellow pine. 



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