SEVENTH ANNUAL MEETING 29 



At present it may be stated provisionally that the laws gov- 

 erning the behavior of substances under stress are the follow- 

 ing: 



First — There is a rapid elastic yield, which, if inertia be 

 'negligible, is practically instantaneous. 



Second — This is followed by a slower yielding which di- 

 minishes with the time and ultimately attains a constant value 

 which may be zero. 



Third — If the stress is released the specimen returns al- 

 most instantly to a point short of its original position. 



Fifth — The behavior depends, in many cases, on the pre- 

 vious stresses to which the specimen has been subjected — these 

 usually tending to strengthen the specimen. 



These experimental results are to be accounted for on 

 theoretical grounds and considerable progress has been made 

 in this direction. 



THE INTERNATIONAL PHYTOGEOGRAPHICAL 

 EXCURSION 



H. C. COWLES, UNIVERSITY OF CHICAGO 



In the summer of 1911, there was organized in the British 

 Isles under the auspices of the British botanists, the first In- 

 ternational Phytogeographical Excursion. This was so suc- 

 cessful in getting plant geographers from various countries 

 together for the purpose of discussion in the field that it was 

 unanimously decided to have a similar excursion in the United 

 States in 1913. The 1913 excursion started at New York on 

 July 26th, and closed at the same city on October 5th. The 

 general route of the excursion included the following places : 

 Niagara Falls, Chicago and the neighboring sand dunes; 

 Lincoln, Akron, Colorado, Colorado Springs, Pikes Peak, 

 Salt Lake City, North Yakima, Tacoma, Mt Rainier, Crater 

 Lake, San Francisco, Mt Tamalpais, Yosemite, Carmel and 

 Cypress Point, Salton Sea, Tucson, the Santa Catalina moun- 

 tains, and New Orleans. 



The excursion numbered from twelve to fifty, depending 

 upon the number of American participants at various places. 

 Ten European members were present at most all of the points 

 visited. Among others, these Europeans included such well- 

 known plant geographers as Professor Engler of Berlin ; 

 Professor Schroter of Zurich, and Mr. Tansley of Cambridge. 

 Professor von Tubeuf, the famous student of trees and their 

 diseases, was also a member of the party. 



