1914] FULLER— EVAPORATION AND SOIL MOISTURE 205 



fact that is emphasized by the presence, very early in its history, of 

 seedlings of Quercus velutina, the dominant tree of the succeeding 

 association. 



In this association, stations 5, 6, and 7 were placed at spots of 

 medium density of growth, about 100 meters south and east of the 

 cottonwood dune series. The averages of the readings from the 

 three stations are plotted for comparison with similar data from 

 the other associations (figs. 4, 5, 6). Compared with that of the 

 preceding association, the rate of evaporation is seen to be much 

 lower and subject to less violent fluctuations. The maxima 

 and minima are nearly synchronous with the preceding and suc- 

 ceeding associations, the most remarkable feature being the very 

 low comparative rate during the weeks of May and October, when 

 the deciduous associations are largely without foliage. The maxi- 

 mum for 1910 (fig. 4) was 17.5 cc. per day, the minimum fell 

 below 4 cc, and the average rate for the season was n .3 cc. daily. 



The next season the maximum rate was 20. 2 cc. per day (fig. 5), 

 the minimum 2.5 cc. per day, and the average 10.3 cc; while in 

 912 (fig. 6) the maximum was only 13 . 7 cc per day, the minimum 

 rose to 4 cc. per day, but the average was reduced to 9 . 7 cc. per 

 day, again demonstrating the fact that 191 2 was a season of moder- 

 ate climatic conditions. 



Proceeding inland from the lake shore, the pines gradually 

 decrease in number, and the black oak (Quercus velutina) becomes 

 more plentiful, until at a distance of about 500 meters south of 

 the last group of stations it forms an almost pure stand, with 

 only occasional trees of white oak (Quercus alba). The shrubby 

 under-growth consists principally of Prunus virginiana, Rosa blanda, 

 Viburnum acerifolium, V actinium pennsylvanicum, Ceanothus amer- 

 icanus, and seedlings of Quercus velutina and Q. alba. Among 

 the herbaceous members of the association are Smilacina stellata 7 

 Lupinus perennis, Tephrosia virginiana, Lithospermum canescens, 

 Asclcpias tuberosa y Helianthemum canadense, Polygonella articulata, 

 and Aster linariijolius. In this oak dune association four stations 

 were placed: nos. 8, 9, and 10 in the stands of average density 

 (fig. 8), and no. 11 in one of the very characteristic openings 

 sparsely covered by xerophytic grasses, together with such plants 



1 



