24 BOTANICAL GAZETTE [JULY 
temperature under which the plant lives from those ordinarily 
recorded (jig. 4). At the top of the figure is given the sunshine” 
SUNLIGHT — 
Lew wrensty | | |e] 6] sl asl als |g | w | as] 67 
Water Consens | 45% | 374 
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Fic. 4.—Variation in temperature at different levels. 
record, together with the light intensity for each hour of the day- 
The water content was determined twice, as recorded in the figure. 
The plant surface temperature record was taken on a mat of : 
Bouteloua oligostachya, and the quadrat was situated on a south 
slope. : 
The extreme conditions at the surface of the soil may account — 
to some extent for the dying of the lower stem leaves, so often noted 
among perennials as well as annuals. : 
Simultaneous readings on north, south, east, and west slopes 
give the curves for soil and soil surface temperatures shown in fig. 5: 
The water content was recorded twice in each quadrat and is als0 
given in the figure; curves of soil temperature are given at the bot 
tom of the figure. Some idea of the temperature at the various — 
levels may be obtained by comparing these curves with those of ; 
jig. 4. The readings shown by figs. 4 and 5 are simultaneous. 14 
Light.—The sunshine records taken show 51 to 80 per cent. of 
possible sunshine. The difference between possible sunshine for 
the forenoon and afternoon is seven to nine hours per month during ; 
