206 DARWINIANA. 



closet botanist. Until this summer I had not seen the 

 Mississippi, nor set foot upon a prairie. 



To gratify a natural interest, and to gain some 

 title for addressing a body of practical naturalists and 

 explorers, I have made a pilgrimage across the conti- 

 nent. I have sought and viewed in their native 

 haunts many a plant and flower which for me had 

 long bloomed unseen, or only in the hortus siccus. I 

 have been able to see for myself what species and 

 what forms constitute the main features of the vege- 

 tation of each successive region, and record as the 

 vegetation unerringly does the permanent character- 

 istics of its climate. 



Passing on from the eastern district, marked by 

 its equably distributed rainfall, and therefore natural- 

 ly forest-clad, I have seen the trees diminish in num- 

 ber, give place to wide prairies, restrict their growth 

 to the borders of streams, and then disappear from the 

 boundless drier plains ; have seen grassy plains change 

 into a brown and sere desert desert in the common 

 sense, but hardly anywhere botanically so have seen 

 a fair growth of coniferous trees adorning the more 

 favored slopes of a mountain-range high enough to 

 compel summer showers ; have traversed that broad 

 and bare elevated region shut oS on both sides by 

 high mountains from the moisture supplied by either 

 ocean, and longitudinally intersected by sierras which 

 seemingly remain as naked as they were born ; and 

 have reached at length the westward slopes of that 

 high mountain-barrier which, refreshed by the Pacific, 

 bears the noble forests of the Sierra Nevada and the 

 Coast Kanges, and among them trees which are the 



