ECOLOGICAL WORK IN BOTANY. 
20 
soil; a relation which seems to have been originally pointed out 
by Schouw in 1823. Warming realized as probably Schouw 
did not, that a grouping based upon a single factor could never 
be a permanent one. He points out that the factors of the en¬ 
vironment are largely mechanical and have aided, but not deter¬ 
mined, the development of the physiognomy of the plant society. 
Besides the name of Warming, we have those of Kjellman, 
Areschoug, Wittrock and many others who have made the botani¬ 
cal literature of Scandanavia largely one of ecological observations. 
Concerning the work of the last ten years in Europe time will 
not permit one to speak specifically. A large amount of work is 
done every year; it is too early to pass judgment on its ultimate 
value. Work like that of Warming, Goebel, and Bonnier will 
endure. Progress is being made every year, but there still remains 
much to be done. 
The first extensive study of the flora of North America seems 
to have been made by Andre Michaux, who between the years 
1785 and 1796 explored the country from Hudson’s Bay to 
Florida and westward to the Mississippi. We may well marvel 
at the completeness of his studies when we remember the diffi¬ 
culties he encountered. Most of the region he visited was an 
unbeaten wilderness where the best of roads were mere bridle¬ 
paths and travel was endangered by the hostile Indian tribes. 
We are indebted to Michaux for a study of the flora of the east¬ 
ern United States before it had been modified by the white man. 
His description of the North American flora, published in 1803, 
was based entirely upon his own collections and does not contain 
any plants which he had not himself gathered or seen. 
Eleven years later, namely, in the year 1814, the second Flora 
of North America appeared from the hand of Frederick Pursh. 
This flora was not confined to the author’s own collections but 
aimed to give a complete description of the plants of North 
America, so far as they were then known. He included in his 
flora descriptions of about one hundred and fifty specimens gath¬ 
ered by Lewis and Clark on their return from the Oregon territory. 
Botany did not become a science in America, however, until 
the time of Asa Gray. He began his botanical work with John 
