(gp 
Insolation and transpiration for kidney beans at Montsouris. 
| Weight of tran- | | Weight of tran- 
spired water | spired water 
Weight divided by— Weight divided by— 
We oftran- |——— +; = . We of tran=| == (7- 1 
Date, 1877. spired | yfean | Mean Date, 1877. spired | wean Mean 
water. | tamper- | actino- water. | tamper-| 2ctino- 
ree | metric | rere | metric 
| degrees. | * | degrees. 
| 
Grams. Grams. 
aly sl Gwe =e 8 Se 0. 686 4.1 1.16 Sully: 240) = so 2 2e=2: 0. 706 3.8 2.00 
ikem ted 0. 422 2.6 1.36 Pal sea et sae 1.300 fiat 2.17 
ioe eee ee 0.727 4.4 1.21 Phe eae eee 0.991 5.3 1.92 
(Geese eeecont Ovb4s 2.9 1.23 Tipe ates 1, 255 6.7 2.46 
ROLE aes Ce 0.577 3.3 - 1.56 CBee seas | 1.426 7.8 2. 64 
rol [ts re oe ie beef 9.1 1.24 3 ee Bees 1.277 5.9 2.97 
ee ee 1. 608 6.2 1.81 BU) ee oe 2.167 7.6 3.55 
(3 )5 eee 1, 204 5.4 1.88 Bile Sete aes 2.710 8.4 3.15 
The figures in the above table are influenced by the quantity of 
moisture in the soil; therefore Marie Davy occasionally omitted the 
evening watering, and the transpiration for the day after such omis- 
sion was smaller. In general, Marie Davy concludes that the relation 
between transpiration and temperature is very variable from day to 
day, while that between transpiration and radiation is very regular, 
x regularity that would very probably be heightened if the cloudiness 
and the evaporating power of the wind, as depending on its dryness 
and velocity, had been considered. The belief is that sunshine excites 
the contraction of the stomata of the leaves and thus stimulates tran- 
spiration; but the stomata can not exude water to a greater extent 
than as supplied by the roots; therefore the transpiration is limited 
by the humidity of the soil adjacent to the roots. Thus on the 30th 
the radiation averaged 45.5 actinometric degrees, and the plant tran- 
spired 2.167 grams of water; on the 31st the radiation was 64.1 and 
the transpiration correspondingly increased to 2.710 grams; but on 
this day the reserve moisture in the soil was drawn upon very heavily, 
and in the evening the leaves of the plant were flabby and drooping 
and evidently wilting for the want of moisture. 
The results by Deherain at temperatures of 15° C. and 0° C. and 
those by Marie Davy seem to demonstrate satisfactorily the slight 
influence of the temperature of the air as such upon transpiration. 
Daubeny (1836), Deherain, and Wiesner have studied the effect of 
radiation in different parts of the spectrum, and their work shows 
that the radiations that are absorbed by chlorophyl, the so-called 
chlorophyl-absorption bands, are those that are efficient in stimulat- 
ing transpiration; also that xanthophyl acts similarly, but weaker 
than chlorophyll; that the violet and ultraviolet have no appreciable 
influence; that the ultrared rays have an appreciable action, but 
feebler than the visible rays between the red and blue, notwithstand- 
