go BOTANICAL GAZETTE [AUGUST _ 
hourly velocity of 11 miles, which is not exceeded during the other 
aspects. Precipitation is slight (7.87°™) and falls on only about 
33 per cent. of the days. The average cloudiness of the sky (4.7) 
is low, and the sunshine (63 per cent.) is correspondingly higher, 
resulting in a low light intensity (0.547). The saturation deficit 
is here not at its maximum (36.3), but, augmented by the high 
wind velocity, evaporation, which must necessarily serve as a rough 
comparative index of transpiration, is rising in amount. While far 
more favorable for vegetation, it becomes progressively more 80, 
the last half of the aspect presenting conditions in soil and ait 
noticeably more congenial to growth. The chresard decreases 
steadily during the aspect from 14.8 per cent. on April 17 to 12 
per cent. on April 25, and a marked difference in holard was evident 
at crest (15.8 per cent.), slope (18.4 per cent.), and base (22.6 per cent.) 
on April 18. The average chresard is 12.8 per cent. 
SPECIES OF THE PREVERNAL ASPECT 
Facres.—None. 
PRINCIPAL SPECIES.—Antennaria campestris,t Carex pennsylvanica,T Peu- 
cedanum nudicaule,} Pulsatilla hirsutissima.* s 
SECONDARY SPECIES.—Astragalus crassicarpus,t Peucedanum foeniculaceum, 
Draba micrantha, Ranunculus ovalis. 
* Not occurring in area proper but in vicinity. + Forming associations. 
The earliest flowering form is Pulsatilla and occurs copiously 1 
subcopiously and characteristically upon the upper slopes of the 
prairie hills. It appears several days earlier upon the south to south: 
west exposure, which holds equally true for the other prevernal 
bloomers. The early warming-up of this exposure accounts for 
above phenological precocity. But the greatest abundance of get 
prevernal forms occurs on the north to northeast exposure. Mature — 
tion follows close upon anthesis, which likewise holds for all prevernal z 
flowering species. of 
Pulsatilla is followed by the blooming, during the first week 
April, of Peucedanum foeniculaceum and P. nudicaule. The formet 
with its umbel of yellow flowers is of rare occurrence; but the Inti?’ 
with its umbel of white flowers appears even copiously in tC 
plats, and in its distribution occurs mainly upon the upper xerophyt s 
