FOREST ZONES AND FORMATIONS 99 



hemlock (T. Mertensiana) is of still narrower horizontal range, 

 being found in this region only in a small part of the Bitter 

 Root and some of the mountains of Northern Idaho. Ordinarily 

 a tree of the high mountains it was found by the writer in the 

 vieinitj' of Wallace at! 5000 feet in association with Pinii^ 

 monticola. Juniperus communis, which forms extensive low 

 thickets at 6500 feet in Glacier Park, is common about Flathead 

 Lake at 3000 and elsewhere at various altitudes. 



Of the undergrowth much the same may be said. A few 

 shrubs Cassiope Mertensiana, Pliyllodoce empetriformis, Salix 

 Barclayi, etc., are found only in the high mountains. Many 

 other species occur freely at elevations from 4000 feet, through- 

 out most of the upper forest belt. Among such the following 



may be mentioned : Pachystima Myrsinites 



Sorbus scopulina Valeriana sylvatica 



Bibes lacustre Erythronium grandiflorum 



Yaccinium membranaceum Calochorhis apiculatus 



" uliginosum Veratrum calif ornicum 



Menziesia glabella Xeropliyllum Douglasii 



Before proceeding to a discussion of the several zones it is 

 desired to call attention to a few facts determined for the six 

 species most important and widely distributed. These figures 

 on the viability of seeds and the rate of growth o!E seedlings are 

 to be interpreted in connection with the behavior of the species 

 in the field. The observations which extend over a period of 

 several >'ears are the results of experimental work by the writer 

 at the University of Montana. The experiments were conducted 

 under the climatic conditions of the prairie, more difficult at 

 Missoula than those to which most of the species are accustomed 

 in their natural situations. Comparisons are made between 

 seeds from different sources. The prosperity of plants in the 

 field is largely measured by their possession of advantageous 

 characteristics among which their seeding behavior and rate of 

 early growth are important. 



The special study of seeds and seedlings pertained to six 

 species, viz., Pinus ponderosa, P. monticola, P contorta, Larix 

 occidentalis, Picea Engelmmmii and Pseudotsuga taxifolia. The 

 seeds were obtained from various sources in California, Oregon, 

 Washington, Idaho, Montana and Colorado, and their behavior 



