216 The Kaj^t WoRtb; 



cubic centimeters from our standard instrument (the names 

 of the stations are shown above the base Hne, which rei~>resents 

 a rate of 100 cc), and the amovmts fcr the different stations are 

 placed upon the graphs. Below tl.e base hne are indicated, 

 by conventional hatching, the ap]:iroximate distribution of the 

 main vegetational types of the areas through which a profde 

 passes. Here are considered: the northwestern, northeastern, 

 and southeastern conifer centers; the deciduous forest; the more 

 or less poorly defined belts of transitic>n between the latter and 

 the two eastern conifer areas; a prairie belt or zone of transition 

 from the deciduous forest to the grass land or plains region ; 

 the grass land area; the California chapparal and the desert. 

 Oui terms are general, our limits merely appioximate,and a host 

 of smaller details explainable on the basis of variations in soil, 

 altitude, etc., are here ignored. Information for our present 

 purpose as to the vegetational typ'cs and their geograihical 

 distribution has been obtained from an unpublished map pre- 

 pared by Dr. Shreve, which he has most kindly placed at our 

 disposal. 



The uppei diagram of Fig. 1 rej^resents a profile of 

 the variations in vegetational types and in the intensity 

 of evapoiation for the summer of 1908 along a line 

 drawn from San Diego to Kaliegh, through Tucson, 

 Dalhart, Stillwater, St. Louis, and Pisgah Forest, the latter 

 station being in the mountains west f f Asheville, X. C. In this 

 diagram the highest intensities cf evaporation are seen to cor- 

 respond aluK st exactly with the limits of the desert region. 

 The California chapparal occupies a strij) near the Pacific, 

 with an a\erage"rate somewhat above 200 cc. per week. From 

 Dalhart to Stillwater there is a raj id dow nward gradient in the 

 summer evaporating power of the air, and the vegetation takes 

 the form of jrairie, or grassland-deciduous forest transition, 

 with an average weekly rate c^f from about 150 to 200 cubic 

 centimeters. The change of vegetation to that of the deciduous 

 forest, as we progress eastward, is not marked by any corres- 

 ponding change in the rates of cxajjoration, St. Louis, indeed, 

 seeming to pcssess a somewhat higher rate than Stillwater. 

 With the very marked depression in the e\a})orating power of 

 the air over the high land at Pisgah Forest, we have a marked 



