1878. | On the Transpiration of Plants. 167 
Fuchsia strong currents of air hastened the process, for while on 
the last day the Fuchsia was experimented with, the temperature 
was no higher and the difference between the dry bulb and dew 
point was not as great as on the previous day, it was found to 
exhale most—exceeding all. the rest of the results by 92 grains. 
This latter excess, under the circumstances, must, in part at least, 
have been due to atmospheric currents, which were more preva- 
lent on that day. The influence of these currents was still better 
exemplified by the results from the Hydrangea. It will have 
been noticed that this plant evaporated, at least an ounce more 
during experiment I. than on any succeeding day. The atmos- 
pheric currents no doubt produce their effect in a mechanical 
manner. They remove vaporized fluid as it is formed, and thus 
really act as a vis a fronte to the vaporizing liquid within. 
Apart from the influence of winds, and given a clear day, a 
glance at the two last tables of results will show a direct corres- 
pondence between the complement of the dew point and the rate 
of transpiration in these cases. This latter fact will become more 
evident hereafter. 
A few observations were made on the Hydrangea with the view 
_of determining the rate of evaporation of different periods during 
the day. It was found that this plant while in the open air evapo- 
rated between the hours of 11 A. M. and 3 P. M. as much as in the 
ant No. 5 was a Camellia japonica, a shrubby plant 28 inches 
high; leaf surface 479 square inches; complete weight of outfit 
ready for experiment, 8 pounds 12 ounces 40 grains. 
The following results were obtained: 
Durationof | Loss of i ths Av’ge | Av’ge | Place of 
Ex, H weight b ‘Itemper-| dew | experiment. Weather. 
: | TEETE iasi 12 pea ature, | point. pi 
I Day and night| 7to gr.| 710 gr.| 78.5° | 63.3° |In ope air Clear. [rain. 
I a 650 * | 650 * | 79.5 | 71-3 Cloudy part, some 
“At “ 170“ 480 «i 90; 61.5 cid Clotigy. clear at piar 
IV R 240“ | Jas | 63. Indoors, (Cloudy. 
-V i 10 “| 190 * |74. | 65.7 5 fini and Bs in 
i xs sho lose 1745 16581 
_ These results exhibit in a satisfactory manner the connection 
between the character of the leaf structure and the aridity of 
~ 
h smaller r quanti of a a we some allowance ae 
