216 LEADING AMERICAN MEN OF SCIENCE 



have included much more than the description of new plants. 

 The unknown field of large geographical distribution thrust itself 

 upon him even at a distance; and it is certain that a personal 

 survey of vegetation in the mass would have made the subject far 

 more real and urgent. In the meantime, however, another oppor- 

 tunity had presented itself, and a choice had to be made. Gray 

 decided to resign his appointment to the expedition; but later its 

 collections came to him for study and he obtained a glimpse of 

 what he had missed. He made the most of this glimpse, for it 

 gave him that large contact with plants outside of North America 

 which always entered into his perspective. 



What he regarded as the larger opportunity was the invitation 

 to become the junior author with Dr. Torrey of the contemplated 

 Flora of North A merica. While waiting for the Wilkes' Expedition 

 to sail, Gray "tried his hand," as he says, upon some of the families 

 for the first part of the Flora, with the result that he was asked to 

 become joint author. It is hard for botanists now to imagine the 

 chaotic condition at that time of descriptions of the North Ameri- 

 can flora. Even for the best known region publication was in 

 confusion; while the vaster western area was practically unknown. 

 To bring together in some definite organization the plants already 

 described, and to describe those brought back by various explor- 

 ing parties in the great west, was the task undertaken by the two 

 authors. With characteristic energy Gray threw himself into the 

 work, and the first two parts about half of the first volume 

 appeared in July and October, 1838. 



At last a definite and congenial position was open to him, for 

 in 1838 he was elected Professor of Natural History in the newly 

 organized University of Michigan. In his work on the Flora, he 

 had become impressed with the necessity of studying the North 

 American plants stored in the great herbaria of Europe. Among 

 them were many of the types, that is, the actual plants upon which 

 the original descriptions had been based. Nearly all of the earlier 

 collections of North American plants were sent to Europe for 

 description; and the subsequent determinations of American bot- 

 anists were based upon descriptions often imperfect and ambigu- 



