de;partme;nt oi? botanical research, 71 



The transplanted culture of Leptinotarsa decemlineata at Tucson has 

 changed in eight generations, so that in the winter time it is unable to meet 

 the conditions of the ancestral environment at Chicago when returned to 

 that city and placed side by side with the original stock. The reason for 

 this is the change in the character of the Tucson population, slowly and 

 progressively, as to the capacity for retaining water in their tissues through 

 the hibernating period, and of giving it up slowly, so that the desiccation of 

 the dry season shall not be fatal. When taken to Chicago and allowed to 

 hibernate in the late summer, which they do naturally, they are absolutely 

 unable to pass the winter alive, owing to the fact that they can not eliminate 

 water fast enough, as the temperature drops, to keep the freezing-point of 

 the tissues below that of the medium. As a result they are killed by the cold 

 of the winter. Like results are now available in some other species from 

 the south which are not able to survive our northern winter for this reason, 

 and this relation persists as a germinal factor in the race. Relations of this 

 nature have played important roles in the distribution and evolution of 

 organisms in nature. 



Of interest in this report are the results obtained in a series of experi- 

 ments originally carried on in duplicate at Chicago and in the desert regions 

 of Tehuacan, Mexico. This latter part was in 1908 transferred to Tucson as 

 the natural desert complex, but met with repeated disaster. The Chicago 

 portion of the experiment, in which an artificial desert complex was brought 

 to bear upon the pure L. signaticollis stock at early stages in the develop- 

 ment of the ova, has resulted in the production in the surviving portion 

 of the experiment of permanent changes in the antennae of a character and 

 degree that if found in nature would be given generic value in taxonomy 

 and one of them of subordinal value, as these things are rated by taxonomic 

 workers. We hope to overcome the technical difficulties at Tucson and there 

 duplicate in nature the results obtained in the laboratory at Chicago. These 

 changes are dominant over the normal form and might well serve as the 

 basis of creating new generic groups by experimental methods. 



The general oversight of the work at Tucson has during the year been in 

 the care of Mr, J. K. Breitenbecker, and much of the satisfactory progress 

 and the present fine condition of the cultures and the plants at Tucson is 

 due to his industry and intelligent aid. 



The Water-content and Activity of Animal Organisms, by J. K. 



Breitenbecker. 



Observations upon the relation of water-content and the functional and 

 habitual activity of organisms under arid conditions have been carried on dur- 

 ing the summers of 191 1 and 1912. Chief attention has been paid to insects, 

 and most of the data have been obtained by a study of the extensive series 

 of Leptinotarsae organized by Prof, W, L. Tower, which have been under 



