82 A Study of the Vegetation of 
Erythromum grandiflorum Leptotaenia multifida 
Fragaria bracteata Lupinus laxiflorus 
Fragaria platypetala Lupinus ernatus 
Frasera fastigiata Moehringia macrophylla 
Galium spp. Pentstemon pinetorum 
Geranium viscosissimum Potentilla blaschkeana 
Helianthella douglas ' Pteridium aquilinum pubescens 
Hieracium albiflorum Sedum douglasii 
Juncoides 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-Larix 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. — 
82 
