1904] SHULL—PLACE-CONSTANTS FOR ASTER 341 
tion being due-to the moderation of extremes of temperature, light, 
etc., the protection from winds, and the consequent maintenance of a 
relatively high degree of humidity. Besides the relative constancy 
of atmospheric conditions, it should be noted that the stream -vhich 
occupies the ravine, and along whose margin the Aster prenanthordes 
is a permanent, spring-fed stream draining so small an 
is growing, 
Fic. 5.—The habitat, looking north. 
“tea as to be little subject to fluctuations-due to the alternations of 
dry "Y and rainy periods. The m map shown in fig. 6 accurately represents 
* Present position of the stream and the location of the areas of 
bir Prenanthoides with reference to it, thus enabling the future 
an stigator to note any changes of area or relation which might have 
an influence upon the variability. 
IV. RESULTS. 
collections having been made about three times a week, 
t does aay {the number of heads which were in bloom at any si 
seem desirable to present curves and correlation tables 
The 
Fe ‘*Sardles, 
