88 
IOWA ACADEMY OF SCIENCES. 
scattered in the forest, but where protected they grow as 
thickly as the Lodge Pole pine. This pine makes a fairly 
rapid growth as is shown in the table on the following page: 
The Bitter Root forest reserve is partly located in Mon- 
tana and partly in Idaho. The eastern part of the reserve 
has its watershed in the Bitter Root valley, in the western 
part of the reserve the water flows to the Clear Water and 
the Salmon rivers. 
It is not my purpose to treat the topography of the 
region as this has been done in an excellent paper by J. B. 
Leiberg. Incidentally Mr. Leiberg"^ touches some ecologi- 
cal phases of this forested area. There is also a good 
account of the ecological phases of the Priest River Forest 
reserve. f Dr. WhitfordJ has given an excellent account 
of the forest region of the Flathead country. 
The drainage of all the streams is of course toward the 
Pacific Ocean. The East Fork empties into the Bitter 
Root river. Warm Springs creek flows into East Fork, the 
Overwhich creek flows into the South Fork and this in 
turn into the Nez Perces Fork which now commonly is 
considered a continuation of the South Fork. The latter 
really terminates at the West Fork. Horse creek 
has its source on the divide between Montana and Idaho 
at an altitude of 8,000 to 8,500 feet. This stream empties 
into the Salmon river. The highest divide continues be- 
yond the old Nez Perces trail. The headwaters of the 
Clear Water reaches the Montana boundary. The rocks of 
this region consist of quartzites and felsitic rocks. Leiberg, 
in the paper referred to, establishes two forest zones, the 
Yellow Pine and Subalpine zones; of the 787,200 acres 
about twenty-six per cent belongs to the latter zone, while 
seventy-four per cent to the former. The most important 
timber species is the Yellow pine, Pmus ponderosa. 
♦The Bitter Root Forest Reserve. U. S. GeoL Survey. 19 : 263. 
tU. 9. Geol. Survey. 19: 217. 
IBot. Gazette 39: 194. 
