112 UNIVERSITY OF COLORADO STUDIES 



North American trees is the Silva of North America by Chares Sprague 

 Sargent, in thirteen foho volumes. The cost of this work, however, 

 makes it impossible for any but the wealthiest individuals and institu- 

 tions to own it. A short work in one volume by the same author is 

 very serviceable. It is the Manual of the Trees 0} North America.^ 

 This book contains illustrations of leaves and fruit of every tree known 

 to grow in North America north of Mexico. General works on botany 

 also contain descriptions of trees. Coulter's Manual 0} the Botany of 

 the Rocky Mountain' Region,'' issued many years ago, is the book most 

 accessible since it is found in every high-school hbrary. Unfortunately 

 the tree descriptions there given do not correspond exactly with the 

 species as recognized today. A useful httle book is Professor Aven 

 Nelson's Key to the Rocky Mountain Flora,^ in which short but accurate 

 descriptions of most of our trees are given. Very useful to the trained 

 botanist is Rydberg's Flora 0} Colorado,'* recently issued. Another 

 important work is a "Report on the Forest Conditions of the Rocky 

 Mountians" by various authors issued as Bulletin No. 2 of the Forestry 

 Division of the United States Department of Agriculture. The second 

 edition of this bulletin was issued in 1889. Professor Sargent's " Report 

 on the Forests of North America" prepared for the Tenth Census ^ 

 contains much information in regard to the commercial value of different 

 trees. Many of the native trees of the Rocky mountain region were 

 j&rst described in the accounts of the early expeditions conducted by 

 the United States government but this material is now gathered in later 

 pubUcations so that reference to these works is not necessary. 



The Pine Family. — As here hmited the pine family in Colorado 

 (Pinaceae) includes the pines, spruces and firs. All bear true cones 

 which become hard and dry, never berry-like as in the junipers and 

 cedars. In addition to the seed-bearing cones there are the pollen- 

 bearing cones which produce the pollen spores in the spring. These 

 are smaller cones; when the pollen has been shed they soon wither 



' Boston: Houghton, Mifflin & Co., 1905, pp. 826. 



' New York: American Book Co., pp. 452. 



3 New York: D. Appleton & Co., 1902, pp. 94. 



* Bull. 100, Agr. Exp. Sla. Colo. Agr. College, Fort Collins, Colo., 1906, pp. 447- 



5 Tenth Census 0/ the United States, Vol. IX, pp. 612. 



