256 M.A. de Candolle on Germination 
have germinated even at a somewhat lower temperature, pro- 
vided the water were liquid; but this kind of experiment ap- 
peared to me too difficult to be attempted*. 
Lepidium and Linum germinated at a mean of 1°°8, but did 
not sprout at 0°. 
Collomia, which does not germinate at 3°, does so at 5°38. 
Nigella, Iberis, and Trifolium repens, which did not germinate 
at 5°°3, sprouted at 5°7. 
Maize, which did not germinate at 5°°7, did so at 9°. 
Sesamum, which did not germinate at 9°, did so at 13°. 
Lastly, the seeds of the melon, which did not germinate at 
13°, did so at 17°. 
Some seeds of the cotton-tree, at least two years old, which I 
thought were beyond the condition for germinating, because 
they had resisted a previous experiment at 18° for several days, 
sprang up when placed upon a stove the temperature of which 
was very variable but at times reached 40°. 
Lefébure decided upon 5° to 6° C. as the minimum for radish- 
seeds placed in a moist soil. MM. Edwards and Colin state 
that they made winter-wheat, barley, and rye.germinate at 7°C.; 
but they do not assert that this is the minimum ; and it is highly 
probable that barley at least would germinate at a lower tem- 
perature by prolonging the experiment. 
Species therefore require a determinate minimum for ger- 
mination. Assuredly agricultural practice would give rise to 
this idea ; but we are not sure whether the germination of seeds 
sown too early in spring is merely retarded, or rendered slower, 
or whether their subsequent development is absolutely impos- 
sible. Experiment shows that in this case germination is im- 
peded ; it also shows how necessary it is, in calculations upon 
temperature in regard to plants, to take as the basis facts deduced 
from constant and prolonged temperatures }, and then to consider 
certain temperatures useless for each species, at least as far as 
relates to germination. Certainly there exist facts in accordance 
with which the same applies to the foliation, the inflorescence, 
and the maturation ; only, these facts are less exact. 
In my experiments, all the species which required the highest 
minima belong to warm countries. They are excluded for this 
reason from cold countries; for if they germinated in them, it 
* Natural philosophers are able to keep water in a liquid state below 0°, 
as shown by M. L. Dufour’s beautiful experiments ; but it is almost impos- 
sible to preserve this state of things, ensuring at the same time sufficient 
oxygen for the germination of the seeds. 
+ M. H. Hoffmann (Witterung & Wachsthum, &c., 1857, p. 525 &c.) 
doubts the existence of a minimum proper to each species; but he confined 
himself to experiments under variable temperatures, the means of which he 
regards as equivalent to a constant temperature. 
