CHAP. VIII. 
SEED. 
301 
than any other at the first dawn of its life. If, says De 
Candolle, the temperature is too high, germination proceeds 
too rapidly, and the result is weak and languishing plants, 
in which we cannot avoid recognising beings too much excited 
and badly nourished. If the temperature is too low, the ex- 
citement is not sufficient, and it often happens that the seed 
cannot resist the decay induced by the water it has absorbed 
but not assimilated. It is between these limits that a suitable 
temperature for every species is to be sought. 
Edwards and Colin have instituted some experiments to 
determine what temperature seeds can bear. They found that 
Wheat, Barley, and Rye could germinate at 7° Cent. 
44°6 Fahr.) ; and that grain of the same description did not 
apparently suffer by being exposed for a quarter of an hour 
to a temperature equal to freezing mercury : such grains were 
afterwards placed in a proper situation, and germination took 
place as usual. Considering that the particles of foecula of 
which seeds consist are not liable to bursting below a tem- 
perature of 75° Cent. (167° Fahr.), these observers were led 
to ascertain how near an approach to this extreme tempera- 
ture might be made without destroying vegetable life. Seeds of 
various cereal and leguminous plants were placed for a quarter of 
an hour in water of this temperature, and they were all killed ; 
five minutes were afterwards ascertained to suffice for the de- 
struction of three in five. Less elevated temperatures were next 
experimented on : Wheat, Barley, Kidney Beans, and Flax 
were killed in 27^ minutes by water at 62° Cent. (143°6 Fahr.) 
a few grains of Rye and some Beans required a longer expo- 
sure to be destroyed. When the temperature was lowered to 
52° Cent. (125°6 Fahr.) most of the seeds in experiment re- 
tained their vitality; but even this was fatal to Barley, 
Kidney Beans, and Flax. 
Fluid water has conducting powers very different from those 
of vapour or of dry air ; it was thereupon important to deter- 
mine whether the temperature that seeds can bear is regulated 
by the nature of the medium in which they are exposed to it. 
In vapour 75° Cent. (167° Fahr.) were sufficient to destroy 
such seeds as were exposed, but at 62° Cent. (143°6 Fahr.) 
they retained their vitality after having been under experiment 
