BOTANY. 



By John M. Coulter. 



Washington, D. C, April 15, 1873. 

 Sir : I have the honor of i>resentiiig to you my report upon the bota- 

 nical specimens collected this last summer. 



1 have separated the botany of the region I traversed into three 

 divisions, sufficiently distinct, in my opinion, to form as many separate 

 floras, and have given their different conditions of soil and climate. 



I have included in my notes upon the mountain-flora a short table of 

 timber-lines, showing the variation^ in the height of the timber-line, 

 depending on the latitude and the presence of elevated plateaus or large 

 bodies of water. The latitude is given with each peak, but the other 

 conditions are so well known it was thought unnecessary to include 

 them. 



I have also added three tables comparing the flora of the western 

 slope of the Rocky Mountains, between latitudes 43"^ and 46°, with that 

 of the eastern slope. The tables were compiled from the collections of 

 1871 and of this last season, and are necessarily imperfect, though they 

 will serve to give some idea of the distribution of phenogamous vegeta- 

 tion on both slopes of the dividing-ridge. 



Of grasses, about sixty species were obtained ; of mosses, fifty-three 

 species ; of lichens, sixty-six species, including varieties, of which one 

 is probably new to science, and two new to the continent. Among the 

 few Fungi collected, two new species have been described by Charles 

 H. Peck, esq. There probably will be in the whole collection nearly 

 1,200 species of plants. 



I wish here to express my thanks for the many favors I have received 

 from botanists. To Professor Thomas 0. Porter were intrusted all the 

 doubtful specimens and new species of Phenogamia, and I am under 

 the greatest obligation to him for his prompt attention and ready 

 response, as well as for the great interest he has always shown in my 

 work. He very kindly consented to make a re-examination of my whole 

 collection of Phenogamia, excejjt the Coniferw, and to correct the mis- 

 takes of inexperience. 



Through the kindness of Dr. George Vasey, I have had access to all 

 the collections at the Agricultural Department, which proved of infinite 

 service. I would thank him also for the interest he took in my work, 

 and for the valuable assistance he repeatedly rendered me. 



Thanks are due also to Henry Willey, esq., Charles H. Peck, Leo 

 Lesquereux, S. T. Olney, George Thurber, and others for the determina- 

 tion of those species to which they have devoted special attention. 



The study of western flora is an immense field open now to all lovers 

 of botany, and many rich harvests are waiting to be reaped by the in- 

 dustrious collector. Hoping that under your auspices in the future, 

 as in the past, much information may be added to our comparatively 

 meager knowledge of western botany, 



I am, very respectfully, your obedient servant, 



JOHN M. COULTER. 



Dr. P. Y. Hayden, 



United States Geologist. 



