32 STUDIES IN THE VEGETATION OF THE STATE 



DISCUSSION OF ECOLOGICAL FACTORS 



With the exception of light and physical water-content 

 factors, observations were taken daily, except Sunday, 

 throughout the period of active vegetative growth, from 

 March 20 to December 7, 1900, in the four locations, prairie 

 or I, thicket or II, open Avoodlands or III, and deep wood- 

 lands or IV. Observations were taken between 5:00 and 

 G:00 P.M. from March 20 to May 5, beginning with location I 

 and ending with IV; between 6 :00 and 7 :00 p.m. from May 5 

 to September 7 ; between 5 :00 and 6 :00 p.m. from September 

 8 to October 26. After the latter date conditions were noted 

 daily from 4 :00 to 5 :00 p.m. During a considerable portion 

 of the time the psychrometer readings were taken at the 

 surface and one meter above the surface of the ground. Be- 

 ginning with July 1 the psychrometer data in the first col- 

 umn represent conditions at the earth's surface, and those 

 in the second column conditions at the height of one meter. 

 In all cases soil temperatures were taken ten centimeters 

 below the surface. 



The direction of the wind, indicated in the factor record 

 by the letters N., S., B., W., N. E., N. W., S. E., S. W., etc., 

 and amount of wind are at best approximations, as no ane- 

 mometer was used. The sky condition for each day is in- 

 dicated by the characters SS 1, signifying few or no clouds; 

 SS I, half overcast; CI f, mostly overcast; and CI 1, entirely 

 overcast. 



Relative precipitation factors were obtained by measuring 

 the rainfall in a vessel partially sunk in the ground, the 

 amount being indicated in each case in centimeters. The 

 physical water-content was determined from samples of soil, 

 taken to a depth of six to ten cm., collected semi- weekly and 

 placed in air-tight tin boxes of known weight. These were 



