DEPARTMENT OF BOTANICAL RESEARCH. 71 



In the report for 1912 mention was made of transplanting cult- 

 ures of L. decemlineata Say from Chicago to Tucson, which had 

 changed in eight generations, so that in that time it was unable to 

 meet the conditions of ancestral habitat at Chicago and was elimi- 

 nated by the winter when returned to Chicago. It has been found 

 that a second culture of L. decemlineata, a pure normal stock which 

 has been in Tucson but four generations, was also entirely eliminated 

 during the winter of 1912-13 at Chicago, thus making it clear that a 

 change in the organism takes place in much less time than that 

 reported in the previous year. At the same time a test was made 

 on the culture whose activities were reproduced in 1912, and it 

 showed no change in its capacities, being entirely eliminated at 

 Chicago. Both of these lines were tested to some extent during 

 October 1912, and it was found that under uniform conditions 

 of desiccation with a temperature of 15° C, the materials from 

 Tucson did not lose water nearly as readily as material direct from 

 Chicago, and the weighings made of materials during October and 

 early November, which were dug up from normal hibernation, 

 showed that on the basis of net drj^ weight the material from Tucson 

 was not losing water with the rapidity that the native material did. 

 This means that the loss of water in the material transplanted from 

 Tucson to Chicago is not sufficientl}^ rapid to enable them to resist 

 the low temperatures of a Chicago winter. The lowest tempera- 

 ture which these beetles encountered in 1913 in their hibernation 

 was -3° C. 



The general oversight of the experiments at Tucson during 1913 

 has been in the care of Mr. G. J. Sinclair, who takes the place of Mr. 

 Breitenbecher, who had charge of the work for the three previous 

 years. Through the year there has been a continued effort to perfect 

 a spherical form of atmometer, with the result that we have now 

 devised a form of standard size, 50 mm. in diameter, with a glazed 

 base both inside and out, and having little or no soluble material in 

 its composition. These were tested out during the early part of 1913, 

 and given a more thorough test during the summer at Chicago and 

 Tucson. Of these, two types have been devised — a white type for 

 permanent use and a black for use in the attempt to measure the 

 effect of the sun's insolation. 



Treelessness in Prairie Regions, by W. A. Cannon. 



Observations on the character, penetration, and variation of roots, 

 and on their relation to the soil environment, particularly as regards 

 water-supply, indicate that in regions of relatively little rain the 

 roots of mesophytic trees usually attain the level of perennially 

 moist soil, that is, soil w^hich is moistened bj^ upward movement from 

 the water-table. This hypothesis assumes that in such regions the 



