at different Degrees of Constant Temperature. 255 
perhaps 44° or 43°, as is proved by the preceding experiment, 
without its being possible to regulate and to determine this limit 
exactly. 
I therefore confined myself to pursuing the trial of the Sesa- 
mum-seeds to about 57°, and the following were the results :— 
A sowing was made, at 7 p.m., in sand which had been slowly 
heated, with the seeds in the dry state, to 51°. I watered 
copiously with water at this temperature. The temperature of 
the soil rose to 57°; it varied from 50° to 57°, mostly remaining 
between 51° and 52°. Some of the seeds were accidentally lost. 
One of five which were left germinated at_the end of twenty-five 
hours and three-quarters. In a final experiment, in which the 
Sesamum, watered in the same way, was exposed to a more fixed 
mean of 43° to 45° for twenty-six hours, and afterwards left at 
temperatures of from 18°°5 to 22°, three seeds out of a dozen 
germinated at the end of six days after sowing; two more fol- 
lowed, and the majority did not germinate, which shows to what 
extent the heat of from 43° to 45° had been prejudicial. 
§ 2. Deductions and Conclusions. 
1. Some seeds germinate at O°. 
MM. Edwards and Colin, in 1834, stated in their memoir :— 
“No seeds are known which are capable of germinating at the 
point of melting ice.” M. de Seynes, in his very interesting trea- 
tise on germination*, repeats, in 1863, “No seeds of the Phanero- 
gamia are known which germinate at 0°.” My experiments 
prove that out of ten species, taken at hazard, one has been found 
which germinates at 0° (Sinapis alba). 
The fact is the more singular, as it does not refer to a plant 
belonging to the polar regions or high mountains. Probably 
there are other species similarly circumstanced, especially among 
those which live in the neighbourhood of snow; but we can 
scarcely become acquainted with this in the ordinary course of 
events. In fact, the persistence of a temperature of O° is very 
rare in nature. <A sun’s ray or the proximity of a body of a 
temperature above 0° is sufficient to raise the temperature of a 
stream springing from melted snow. It is well known how 
difficult it is to maintain a temperature of O° in a basin filled 
with ice, when it is required to verify the zero-point of a thermo- 
meter. Only by attentive observation in a prolonged experiment 
can it be determined whether a species germinates at 0°. There 
are even some seeds for which an experiment lasting thirty-five 
days, like mine, is not sufficient. 
2. Necessity of a minimum for each Species. 
Sinapis alba germinated at 0°. Perhaps this species might 
* De la Germination, 8vo, Paris, 1863. 
