et 
Another study into the total radiation received by the plants in 
sunshine was made by Gasparin by placing a thermometer in the cen- 
ter of a globe 1 decimeter in diameter, made of thin copper and cov- 
ered with a layer of lampblack. Having found by comparison that 
bulbs of different sizes gave different temperatures, he recommends 
this size to all meteorologists; but I do not know of observations 
wade by others until Violle (1879) urged the same construction and 
size for his conjugate bulbs. This bulb in the full sunshine and at a 
standard distance above the ground seemed, to Gasparin, to give 
what he calls the temperature of a dry opaque body. The differ- 
ence between this and the temperature of the air gave a surplus show- 
ing the effect of solar radiation on the leaves; again, the difference 
between this dry, black bulb and the temperature of the surface of 
the moist earth gave him some idea of the nature and amount of the 
influence of the Shae on the surface of the soil, which he illustrates 
by the following table, derived from seventeen years of observations: 
Temperature at 2 p.m. 
Black | | Black 
Month. Soil. | bulbin Month. | Soil. | bulb in 
the air. the air. 
STU AT Vee ee See ae eae 6.7 SSS GA eyo f= 00) ri ae i a a ee 43.1 44.1 
Re pruarcy mime mans thas 122% 22.0" || September 2-22.) as 31.4 38.9 
Ure 0) ER Ee RS ee eee 19.1 28.5 | OCtO DET aa ee a eee 20.2 28.7 
JN Oy eile a a Re i ee eae 25.5 29. 4 | INOWeM bores = sas ees ee ee 12.1 | 19.4 
SUE Ses Bs Aa ante Sa ha Se 27.6 3424. ||*" December tee. —-- so. see 5.9 | 15.4 
June --.---.2-.--------.--.---- 40.9 39.4 | Mevorisoser. nie oe 24.4 29.6 
ONIN S Ste ae ee ee ee ee 45.3 43.4 | 
| 
On this table Gasparin remarks: 
We see how much the difference of temperatures of the stems and 
the roots ought to modify the flow of the sap, and there is here an 
interesting subject for physiological study which should redound to 
the profit of agricu‘ture. The solar heat contributes also in a remark- 
able manner to cause the differences in the vegtation of the moun- 
tains and the plains. On mountain tops it is the heat of the surface 
soil and the roots in the sunshine and the effect of sunshine on the 
leaves that makes possible the existence of a great variety of pheeno- 
gams. The direct action of the solar heat is the explanation of the 
possibility of raising cereals and other southern crops in high north- 
ern latitudes. 
Gasparin (1852, p. 100) gave the following table, compiled for west- 
ern Europe, showing the mean temperatures of the day during which 
the respective plants leaf out, flower, or ripen. This early Sine. to 
apply meteorological data to the study of plants takes no account, as 
the author himself says, of other meteorological conditions than tem- 
perature such as introduce considerable variations into the phznolog- 
ical phenomena, but he gives it in hopes of helping thus to fix the rela- 
