1878. ] On the Transpiration of Plants. 169 
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7 
to be most rapid about noon and a little after; and it was found 
here, also, that half the quantity evaporated by day was given off 
between the hours of 11 A. M. and 3 P.M. These observations 
were made on clear days. 
The last, or plant No. 7, was a Dracæna, an herbaceous plant ` 
_ with large leaves (being cultivated for its foliage). Its leaf sur- 
_ face was estimated at 817 square inches; its height 27 inches; 
weight not taken; complete weight of outfit, 11 pounds 6 ounces. 
The following are the results obtained : 
i 
q 
| | | 
D | Loss of | Loss by Aver’ ge ae 
Aai pi no ees ht by| day, ltempe | Place. Weather. 
evaporatn| 12 hours. | Ene boi fe | 
i | 
Day and dightloyBe gr. 2410 gr.| 607 T gage ‘In open air Clear. 
II “ [1870 * 11385 * | 64 4-4 
7 Clo oudy, clear at night. 
x ise f | cit | PG ORR | fs Clear, kait Bien 
Ai |2670 * |2410 “ | 79.5 | 66.6 3 Clear , do, 
ya |2770 “ 12620 792 OO. 4 i Clear, mek kiad 
, In comparison to the extent of leaf surfacẹ, this plant did not 
_ transpire as fast as most of the other plants used. The fact of the 
_ Draczena having smooth and. more or less hard leaves, no doubt 
_ In experiments IV and V, with both the Lantana and Dracena, 
are shown once more the favorable influence of winds over this 
_ process in plants. The scales used in all these experiments were 
accurately adjusted. 
Summary of Investigations. 
In clear weather the evaporation by night as compared to that 
which takes place in the day appears to be about in the ratio of 
Ito 5. In some cases no loss occurred on dewy or cloudy 
nights. The Camellia, however, lost nothing during clear nights, 
and gained in weight on dewy or rainy nights, even when kept 
indoors. Under ordinary circumstances evaporation at night 
periments, half was given off between the hours of 11 A. M. and 
P. M., as shown by repeated G testing. 
