THE United States Geological Survey has already issued in the form of reports various papers dealing with the conditions of the localities in the more important forest reserves. Professional Paper No. 29 of the forestry series of the department deals with the forest conditions in the Absaroka division of the Yellowstone Forest Reserve, Montana, and the Livingstone and Big Timber Quadrangles. This report first treats of the location, extent, and topography of the Yellowstone Reserve. The forest itself is almost wholly coniferous, consisting of pines, spruce, silver and Douglas firs. A most interesting account is given concerning the distribution of these species, especially in regard to altitude and aspect. As regards the ages of the trees the greatest diversity prevails. Age classes occur, varying from 55 to 20 years, 75 to 100 years; also stands from 200 to 300 years old are represented, this condition of things having been brought about by fire, the different age-classes corresponding to burns of different periods. The character and volume of merchantable timber are next carefully gone into. These naturally vary according to the species of tree, as well as the altitude and aspect in which it is growing, and the report brings out very interesting facts in this connection.