210 CLIMAX FORMATIONS OF WESTERN NORTH AMERICA. 



lodgepole consociation was found to be 0.08 to 0.07, while germination was 

 only fairly good at 0.2 to 0.14 (Clements, 1910 : 40). The values of yellow 

 pine and limber pine (Pinus ftexilis) are not very different, though such 

 forests are usually more open. Douglas fir is much more tolerant, reproduc- 

 ing readily in values as low as 0.04, while the mature forest may show intensi- 

 ties below 0.01. 



As would be expected, the serai sequence conforms to the water and light 

 demands. Pinus ponder osa is everywhere the earliest of the three major 

 dominants, and is followed by Pseudotsuga, and this a little later by Abies 

 as a rule (Clements, 1905 : 270). Pinus contorta is the universal subclimax 

 dominant of burns everywhere from central Colorado northward into Alberta 

 and British Columbia. In the Rampart Range, about Pike's Peak and south- 

 ward, its role is taken chiefly by aspen. Picea pungens is generally somewhat 

 subclimax in moist valleys and canons, while the remaining pines resemble 

 Pinus ponder osa in their general successional relations (plate 49). 



SOCIETIES AND CLANS. 



The following lists are for the central Rocky Mountains and are based 

 chiefly upon studies made in Colorado (Clements, 1904 : 8). Rydberg (1915) 

 has given comparative lists of the herbaceous flora of the different regions, and 

 Shreve (1915 : 32, 35) has noted the characteristic species of the pine and fir 

 forests of the Santa Catalina Mountains of Arizona. The majority of the 

 genera in the latter are those of the central region, though the species are 

 largely different. The central and northern areas are seen to resemble each 

 other closely in the important species, when it is recognized that the transition 

 region of northwestern Montana and northern Idaho belongs rather to the 

 Coast forest. Because of the shortness of the season, it is convenient to dis- 

 tinguish but two aspects, a vernal and an estival. 



Societies: 



Shrubs — 



■ Acer glabrum. 



Betula occidentalis. 



Prunus pennsylvanica. 



Cornus amomum. 

 Herbs — 



Fragaria vesca. 



Viola biflora. 



Mertensia pratensis. 



Besseya plantaginea. 



Clans: 



Actaea rubra. 

 Habenaria stricta. 

 Erigeron glandulosua. 



Societies: 



Thalictrum fendleri. 



Galium boreale. 



Geranium caespitosum. 



Geranium richardsonii. 



Castilleia miniata. 



Erigeron asper. 

 Clans: 



Allium cernuum. 



Solidago oreophila. 



Vernal Aspect. 



Opulaster opulifolius. 

 Ribes lacustre. 

 Arctostaphylus uva-ursi. 



Heuchera parvifolia. 

 Pseudocymopterus montanus. 

 Pentstemon gracilis. 

 Pentstemon secundiflorus. 



Pirola chlorantha. 

 Smilacina stellata. 



Estival Aspect. 



Jamesia americana. 

 Rosa acicularis. 

 Viburnum pauciflorum. 



Washingtonia obtusa. 

 Aralia nudicaulis. 

 Atragene alpina. 



Viola blanda. 

 Calypso borealis. 



Arnica cordifolia. 

 Gentiana amarella. 

 Potentilla glandulosa. 

 Pirola uliginosa. 

 Saxifraga bronchialis. 

 Heracleum lanatum. 



Pirola secunda. 

 Androsace septentrionalis. 



Valeriana silvatica. 

 Senecio cernuus. 

 Haplopappus parryi. 

 Gentiana affinis. 

 Streptopus amplexifolius. 

 Aquilegia coerulea. 



Galium triflorum. 

 Peramium ophioides. 



