4 6 



WILD FLOWERS AND TREES OF COLORADO 



and southern trees which do not now exist in the state at all. Among 

 these others were: mulberry, soapberry, acacia, redbud and walnut. 

 No doubt the climate was much warmer at that time and, in the 

 mountains at least, more moist. The fossil imprints of many of the 

 leaves are very perfect and the trees can be told with considerable cer- 

 tainty. We may be sure that for thousands and perhaps millions of 



Fig. 41. — Sub-altine Forest of Englemann Spruce 



years the pines, cottonwoods, cedars and thornapples have been an 

 important part of the vegetation of this part of the world. 



Literature dealing with Colorado trees. — The well-known manuals 

 of botany of the eastern United States..such as Gray's and Britton's, 

 describe certain of the tree species of Colorado. So, also, the Rocky 

 Mountain Botany 1 by Professor John M. Coulter, issued many years 



1 A new edition of this work, rewritten by Professor Aven Nelson of the University of Wyoming, is to 

 be issued in 1010. 



