at different Degrees of Constant Temperature. 253 
Temperature of about 28°. 
Being unable at Geneva, even in a very hot summer, to 
obtain in the open air constant means above 24°, I had recourse 
to artificial heat for the higher temperatures. 
A basin, nearly filled with warm water, was placed upon a support 
heated by a lamp, which required to be renewed only three times 
in twenty-four hours. A porcelain cup filled with sand was im- 
mersed two-thirds in the water of the basin to receive the seeds. 
The temperature remained pretty constant between 29° and 80°. 
I then sowed the seeds, at an equal distance from the edge of the 
cup, and, after having allowed them to acquire the temperature 
of the sand, I watered them well with water at 80° which had 
not been boiled. The experiment, which was begun at midnight 
on the 2nd of August, was stopped at noon on the 6th. During 
this period, the mean temperature of the room fell from 21° to 
18°. This cause, as also the evaporation from the more or less 
moist sand, and the unavoidable alterations in the source of heat, 
induced a variation of temperature from 27° to 29°, and in 
the morning of the last day it fell to 26°°3; but this could not 
have had any influence upon most of the seeds, which had already 
germinated. The results were: 
Lepidium. Two seeds germinated in thirty-nine hours; one or 
two others sprouted afterwards; but most of them did not ger- 
minate. 
Linum. One seed germinated at the end of two days and a half; 
at the end of the third day three only had germinated; the 
majority, about four-fifths, did not germinate. 
Maize. Up to the thirty-sixth hour single seeds sprouted, 
but after the second day almost all the seeds sprouted vigorously. 
Melon. One seed evolved its radicle at the end of the third day, 
and at the end of the third day and a quarter the majority ger- 
minated regularly. 
Sesamum. The germination began at the end of twenty-two 
hours ; it was abundant during the three or four following hours. 
Sinapis. Two seeds only out of ten germinated at the end of 
the third day ; six hours afterwards a third showed its radicle ; 
most did not germinate. 
Trifolium. Some seeds germinated at the end of the third day; 
most did not germinate. 
Collomia and Nigella did not germinate. To prolong the ex- 
periment, I left these seeds as they were, but under such con- 
ditions that the temperature varied from 82° to 87°, until the 
10th of August. Two or three of Trifolium and one or two of 
Linum sprang up, but neither Collomia nor Nigella. 
On the 4th of August, at 5 p.m., I sowed and watered some 
seeds of Sesamum in a little cup placed so as to maintain a tem- 
