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UNIVERSITY OF COLORADO STUDIES 



and cedars; they have flat scale-shaped leaves. Now with specimens 

 of the twigs and cones at hand turn to the " Key to the Colorado genera 

 of the Pine Family" on p. 115. Read what is given after A and after 

 B, If the specimen agrees with the description A it belongs to the 

 genus Pinus, the pines, and the particular species may be learned by a 

 study of the key to that genus on p. 116. If the specimen is not a pine it 

 will be described by the paragraph B. In that case read a and b. If 

 the description a is satisfactory the specimen is a true spruce of the 



Leaves of the Different Genera 



1. Pinus; 3. Pseudotsuga; 3. Picea; 4. Abies. 



genus Picea and the species may be determined by a study of the key 

 to that genus. In like manner, if the specimen belong to either of the 

 other genera, that fact will be apparent on reading down the key ; refer- 

 ence may then be made to the appropriate key for fuller information 

 and for determination of the particular species. Sometimes it is impos- 

 sible to secure cones but even then the genus may be determined and 

 the tree identified as a pine, spruce, Douglas spruce or fir. In fact the 

 species itself may usually be told without the cones, especially when the 

 tree is a typical one of its species. 



