THE NORTH TEMPERATE ZONE 115 



require more moisture than those of the open plains. There 

 is also an infusion of high mountain species, which mingle with 

 those belonging to the dry prairie. 



A feature of the Colorado mountains are the "parks,' broad, 

 grassy, nearly level valleys lying between high mountains. Estes 

 Park is familiar to tourists, and is a good example of this forma- 

 tion. 



These parks are fairly level valleys having an elevation of 

 6,000 to 10,000 feet. The grassy meadows are rich in beautiful 

 flowers, most of which are true sub-alpine types and quite dis- 

 tinct from the plains flora. 



The Rocky mountain flora while having a good deal in common 

 with the alpine floras of Europe, differs in many details. The 

 gentians, campanulas and primroses, are much less in evidence, 

 while on the other hand, American genera, e. g., Castilleia, Pent- 

 stemon, Mimulus, as well as Aster and Solidago and some other 

 Compositae, are very abundant, both as to species and indi- 

 viduals, and these are mostly absent from the European moun- 

 tains, or in the case of the Compositae, much less developed. 

 One of the finest of the mountain flowers is the great blue and 

 white columbine (Aquilegia coerulea) the state flower of Colorado. 



Above the parks the mountain sides are in many places clothed 

 with a fairly heavy forest mostly of conifers. On Pike's Peak 

 the timber line ascends to 11,500 feet. The forest is composed 

 of several species. The yellow pine (Pinus ponderosa, var. sco- 

 pulorum) is abundant above 6,000 feet, usually associated with 

 Douglas fir (Pseudotsuga), these being the most widely distributed 

 of the western conifers with the possible exception of the lodge- 

 pole pine (P. Murrayana). Over large areas the Engelmann 

 spruce (Picea Engelmanni) is the predominant tree, and is wide- 

 spread in the Rockies, but scarcely reaches the Pacific coast. 

 This species ascends to the timber line, occasionally over 12,000 

 feet. In the higher altitudes, the yellow pine gives place to the 

 limber-pine (P. flexilis), which reaches its best development further 

 north. The alpine fir (Abies lasiocarpa) also reaches timber line, 

 and lower down the Pacific white fir (Abies concolor) is met with, 

 but never reaches the dimensions attained in the Pacific forest. 

 On the dry slopes low bushes of juniper are common, as else- 

 where in the western mountains. 



