FOREST FORMATIONS AND FOREST TREES 51 



black walnut and hardy catalpa. Rock pines are especially desirable 

 for hillsides and in poor soil. The deciduous trees are more often 

 planted in the fine-grained soil of the plains region. Unless grown 

 on bottom lands all trees planted in Colorado must be irrigated or 

 else well cultivated and protected during the first few years after 

 being planted. 



Scope of the present study. — The following pages are given up to 

 keys for the determination of the species of trees in the state, together 

 with a somewhat full account of each of the trees of the pine family. 

 It was thought best to describe these trees in some detail on account of 

 their economic value and the general interest which attaches to them. 

 It is impossible at the present time to state fully the distribution of most 

 of the species within the state. Only a small part of the area has been 

 examined by botanists so that the limits of distribution are imperfectly 

 known. 



How to use the keys. — It is necessary to look at Key I for the "ever- 

 greens" (trees of the pine family) and at Key II for any other trees. In 

 each of the keys two choices are open to the student at first, named 

 respectively ia and ib. These two are to be read carefully and which- 

 ever describes the tree under consideration will be used as the beginning 

 of the classification. At the right of line, is a figure in parenthesis 

 which refers the user of the key to the next line which is to be 

 consulted. This may give at once the desired name or it may 

 refer to a still lower line. At any rate the process is to be continued 

 until the name of the genus is found. Noting the number of the 

 genus, as well as the name, the student should now turn to the proper 

 place in the following pages and, with the aid of the special key, deter- 

 mine the exact species. Both the scientific and English names are 

 given since both are likely to be useful to one interested in botany or 

 forestry. 



KEY I. FOR IDENTIFICATION OF COLORADO EVERGREENS 



1 a. Trees with needle-like foliage leaves; fruit a cone. (2) 



ib. Trees with scale-like, overlapping leaves, fruit a small berry (cedars). 



Genus 5. Sabina 



