35 
Trifolium repens: Very few seeds germinate at 28° C., and prob- 
ably none at 30° C. 
Mays: Probably the upper limit is 35° 
minated after being exposed to 50° C. 
Melon will stand 40° C., but it is probable that above 42° C. ger- 
© 
C., although one seed ger- 
mination is impossible. 
Sesamum will stand 40° C., and possibly 45° C., the latter being the 
upper limit. 
These upper limits, as I have before said, depend very much on the 
moisture, and on account of the difficulty of the experiment I have 
not endeavored to obtain great exactness. 
Lepidium and Linum: According to the experiments of Burck- 
hardt, some of these seeds have germinated after an immersion of 
half an hour in water at 50° C., but not after half an hour in water 
at 60° C. 
Raphanus sativus (radish): Lefebure shows that these seeds ger- 
minate in moist earth at a maximum temperature of 38° C. 
Triticum (winter wheat), 7riticum (spring wheat), Hordeum 
(barley), Secale cereale (rye), and Avena (oats) germinate per- 
fectly at 40° C., partially at 45° C., and not at all at 50° C. 
(4) The range between the maximum and min’num temperatures 
at which germination is possible differs appreciably for these various 
species. Evidently a small range is a condition unfavorable to an 
extensive geographical distribution. 
(5) Marked differences are observable between seeds of the same 
species and coming from the same place. This is well known to the 
farmer and strongly affected some of the preceding observations. 
The seeds of the same plant or the same capsule are not identical 
physically nor chemically. But if the temperature and moisture are 
those most favorable to germination, many seeds will sprout simul- 
taneously, whereas near the maximum, and especially the minimum, 
temperature the seeds germinate very irregularly and many of them 
not at all. 
(6) The structure of the seeds, especially the presence and nature 
of the albumen within them, ought to exert a definite influence, but 
the small number of species that De Candolle experimented upon 
does not allow of extensive generalizations. 
The species having little or no albumen—viz, Sinapis, Lepidium, 
and Linwm—germinate at very low temperatures. Those having the 
next larger amounts of albumen—viz, Nigella, Collomia, and Zea 
mays—germinate at about 5° C.; but Sesamum, which has but little 
albumen, requires 10° or 12° C. 
At 17° or 18° C. all these seeds germinate well, but the length of 
time required increases somewhat as the albumen increases, showing 
that the latter exerts a retarding influence. The order of germina- 
