202 BOTANICAL GAZETTE [MARCH 
mum, and mean monthly temperatures for a period of forty years, 
were compiled from data given by Moster.? It will be noted that 
the rainfall is adequate and is well distributed throughout the year. 
The average data of the last killing frost in spring is April 26, and 
that of the first killing frost in autumn is October 16, giving an 
average growing season of 173 days. 
Sort.—The soil of the forest is yellow-gray silt loam, an upland 
timber soil.3 There are no streams within the forest, but the 
region is drained by a tributary of the Salt Fork of the Vermillion 
TABLE I 
WEATHER CONDITIONS AT URBANA DURING I919 
pagconchag Rain- aie tebe No. oF 0. ut No. oF 
1919 : a i ee : CLEAR | Pre py | CLOUDY 
ee meng: | Mean: | tina | Mom | renee, Dee | Oke ears 
January. . 55 S| 34.2 | Gar) 76.4 | 75 | SW 16 6 9 
February 56 Tt 1 ar6-) F028) 97.6 | St NW 10 3 15 
arch. . 67 9 4.01 4.19 7 76-5 | 3.015 13 6 12 
Ante oo 76 4° 1 5s.2 1 0,98 | 26.9 16.5 SW. 7 6 17 
Mee 3s 92 38 | 60.8 | 3.29 | 78.6 | 7.4 | NE 8 7 16 
ee gl $2) | 75.5 | 6:90 1 990-9 | 5.8 | SE 10 13 7 
Te es 96 56 | 81.3 | 2.66 | 50.3 | 6.1 | SW 23 8 ° 
August....] 94 SO | 73.91 3.85 | 63.4 | 60.4 | SW 19 9 ie 
September.| 92 a2 | 70.5 | 4.47 | 68.47 6.2 TSW 19 5 6 
ere) BS 33° | 58.4 1 5.50 1 79.8 | 7.0 | SW II I 19 
November.| 63 0°") 30.3 13°47 | 98.3 1 8.9 SW 12 5 13 
December.| 51 |— 4 | 23.9 | 0.12 | 77.6] 7.4 | SW 9 3 19 
pa | Seay Po ro cman SOE Ce) a ie iy aac arr 157 42.119 
Average.| 76.8 | 26.6 | 53.4 | 2.04 | 74.2 | 7.7| SW | 13.1] 6 11.3 
River. This ditch flows in an easterly direction some forty rods 
south of the present boundary of the forest. The forest itself is 
only gently rolling, but several acres in the middle eastern portion 
are several feet lower than the highest parts of the woods, and in 
the lowest part there is often standing water for a few weeks in 
ring. 
As will be shown later, the vegetation in the lower part of the 
woods is quite different from that in the higher parts, and this 
difference seems to be almost entirely due to the difference in the 
2 Mosier, J. G., Climate of Illinois. Univ. Ill. Agric. Exp. Sta. Bull. 208. 1918. 
3 Hopkins, C. G., Moster, J. G., VAN ArsTINE, E., and Garrett, F. W., Cham- 
paign County soils. Univ. Ill. Agric. Exp. Sta. Rep. 18. 1918. 
