at different Degrees of Constant Temperature. 257 
would be too late in the spring, and the ripening of the seeds 
would not take place before winter. Among those species which 
germinate at low temperatures, some belong to temperate coun- 
tries. They do not advance so far as the polar regions, either 
from causes not relating to germination, or because, germinating 
too soon, the herbaceous parts are attacked by the cold. 
3. Existence of a maximum. 
When the temperature remains at a certain rather high degree, 
some seeds are no longer able to germinate. Thus, in my ex- 
periments, the seeds of Nigella and Collomia did not sprout when 
the mean exceeded 28°. Most of the seeds of Trifolium repens 
did not germinate at 28°, whence it might be supposed that at 
about 30° none would have sprouted. Maize must cease at about 
35°, for at 40° the seeds became brown and as if burnt. One, 
however, of the seeds which had been rendered brown by a heat 
of 50° to 57°, germinated on the eleventh day, when, the experi- 
ment having been abandoned, the temperature fell to 18° or 20°. 
The seeds of the melon and, especially, Sesamum bear 40°; but 
they assume a brown tint, which indicates a certain change, and 
it is probable that at about 42° in the case of ,the former, and 
45° in that of the latter, germination would usually be impossible. 
However, some of the Sesamum and melon-seeds which had 
reached 45°, and were subsequently left at 18° to 20°, sprouted. 
As stated above, the limit depends greatly upon the moisture. 
When long immersed in water at 50°, and even 45°*, many of the 
seeds would suffer. They are still capable of germinating in moist 
earth; and as the quantity of moisture is very variable, and 
this could not in my experiments be observed at each degree 
of elevated temperature during a somewhat considerable length 
of time, I did not attempt to obtain greater exactness. 
Lefébure fixed the maximum for the seeds of the radish sown 
in moist earth at 38°C. MM. Edwards and Colin found that 
all the seeds of winter-wheat, spring wheat, barley, rye, and oats, 
sown at 40° in slightly moist sand, sprouted, that at 45° only a 
part of them did so, and at 50° none germinated. 
4, Amplitude between the minimum and the maximum. 
If we designate as amplitude the number of degrees between 
the minimum necessary for the germination of a species and the 
* None of the seeds of the Leguminosze and Graminacez submitted to 
experiment by MM. Edwards and Colin were capable of germinating after 
immersion for a quarter of an hour in water at 50°. According to M. F. 
Burckhardt’s experiments, the seeds of Lepidium and linseed were sus- 
ceptible of germination after immersion for half an hour in water at 50° 
(49°°6 to 51°'4), but not for the same period in water at 60° (57° to 62°). 
Ann. & Mag, N. Hist. Ser.3. Vol. xvi, 
