diversity. It extends from the benches and plains at '2000 to, 

 :;ooi) peel t<> tin- level of continuous forest at 4000 to 6000. Tt 

 may thus fivin < nc part cf the region to another cover a vertical 

 distance of 4000 feet. It is largely the foothill country, varying 

 with exposure and location from arid to humid conditions, inter- 

 rupted and divided here and there by descending extensions; 

 of tin- montane forests. In some places it is the bunehgrass 

 ' . t '// t,[ii/fnn \/>/>J 01- the bunchgrass and sagebrush (Art<ntisi<t 

 tridi iiltitu, A. cdixi. A. fri(/i(l<i. <tc.) or these merging into open 

 stands of Rocky Mountain juniper, or yellow pine or Douglas 

 spruce, or all of them intermingled. Again it appears in areas 

 in composition similar to the Pacific Coast Humid Transition 

 with hi mlock. grand fir. arbor vitae, western yew and many 

 other forms commonly found in the forests of the low lands of 

 western Oregon and Washington. The humid forest is the 

 more rare and is developed where neighboring areas are elevated 

 to the degree necessary to induce condensations and abundant 

 rain, where the valleys are not too wide and where the proximity 

 of considerable bodies of water and the structure of the soil 

 combine to afford the requisite conditions. These are forests 

 of moderate or low elevations, L'000-4000 feet. The forests of 

 the Transition alternate frequently with prairies and the vege- 

 tation of this zone extends in the southern part of .Montana 

 about 1000 feet liiuher on the mountain sides than it does in the 

 north, reaching even to b'ooo feet. 



The forest of the foothills (Transition;) merge gradually 

 into those of the montane (Canadian) belt. Especially in 1 In- 

 humid forest is the line of denial-ration uncertain. KYIVreu -e 

 to the tables under the discussion of general aspects of distri- 

 bution will show that in most sections the vertical ran ire ef many 

 Species may be LlOOO to 4000 feet and in different parts of the 

 slat.- BOme species may be found at altitudes varying from L'OOO 

 to "" (l() feet The following figures indicate the approximate 

 extent of vertical distribution of the species cf gymim>perms 

 within this region, as far as at present known. 



