48 ^ThE l^LANT WoRtb. 



lings of Cticumis, Ipomoea, Mirabilis, Phaseolus and other 

 annual plants. It is shown that as a result of being grown 

 in a humid atmosphere, all the plants studied acquire a much 

 greater than normal capacity for transpiration in a moderately 

 dry atmosphere, but that different families and different genera 

 of the same family vary greatly in theii capacity to acquire by 

 such culture a tendency to extremely rapid transpiration. 



The Distribution and Movements of Desert Plants, by 

 Volnev M. Spalding, has been issued as pubhcation No. 113 of the 

 Carnegie Institution of Washington. The first part is devoted 

 to a consideration of the plant associations and habitats of a 

 restricted area in which the domain of the Deseit Laboratory at 

 Tucson, Arizona, is situated. 



The second part discusses the local distribution of certain 

 species on this area, and includes comparative observations 

 made in other parts of the vSouthwest. In this division of the 

 work an attempt is made by means of exact mapping of the dis- 

 tiibution of important species on restricted areas, by numerical 

 data, and by determination of the value of certain physical fac- 

 tors, to airive at conclusions regarding the causes underlying the 

 most obvious facts of distribution, such, for example, as the 

 marked differences in choice of habitat manifested by the mes- 

 quite and creosote bush, the several species of palo verde and 

 others. The percentage of available soil water, temperature 

 relations, determined in part by aspect, amount of alkali in the 

 soil and the capacity of the latter for aeration, are named as 

 determining factors. The correspondence between topographic 

 features as the result of physiographic processes and the local 

 distribution of plants is strikingly brought out in the compara- 

 tive studies, especially those conducted in the Gila Valley. 

 No less important are the observations of the close correspondence 

 between different rock formations and the well-marked plant 

 societies supported by them, as recorded by Blumer in his studies 

 of the Fort Bayard (New Mexico) watershed, in which, within a 

 comparatively limited area, no less than seven distinct societies 



