in Reply to M. DeCandolle. 493 
comme on la dit *, unedes conditions nécessaires a la germina- 
tion: il n’y a personne, en effet, qui n’ait vu des graines ger- 
mer, quoique exposées a la clarté ft.” Yet this objection is 
equally invalid with the objection that was made to the 
maturity of the seed. I do not say that a seed may not ger- 
minate if left exposed to the light. I do not say that it may 
not be made todo so. _ But is that giving it a fair chance for 
early and healthy germination? Is that treating it in a way 
to bring all toasuccessful issue? For, again, I allude merely 
to the operations of the farmer and gardener, and not to the 
experiments of the chemist in his closet ; though I am ready 
to admit that there is, perhaps, no rule without its exception ; 
and on this ground it will be easy to find a flaw in almost any 
rule whatever. Suppose a writer on agriculture were to say 
that it is necessary for the cultivator who would farm well 
to keep his corn-fields clear of weeds; the truth of the rule 
might be denied by any one who was disposed to be captious. 
For he may turn round upon the rale-maker, and say,— No 
such thing! What you advance is not the fact, for I have 
seen many a good crop of corn in fields where the weeds stood 
higher than the corn itself. This may be all very true; but 
would it be a good and valid objection against the keeping of 
corn-fields clear of weeds? Certainly not. What then are 
we to think of the objections with which M. DeCandolle com- 
bats the accuracy of the above conditions of germination ? 
For in the one case he admits that the grains selected for sow- 
ing should be the largest and the best nourished,—but how 
can they possibly be so, unless they are left upon the stalk 
till they are fully ripe?—and in the other case he does not 
deny that the exclusion of light is useful to germination, he 
only denies that it is necessary. But if it can be shown to 
be useful, we maintain that it is on that very account practi- 
cally necessary. 
III. <A third condition of germination is the access of a 
certain degree of heat. No seed has ever been known to ger- 
minate at or below the freezing-point. Hence seeds do not 
generally germinate in winter, even though lodged in their 
proper soil. Yet the potential vitality of the seed is not 
necessarily destroyed by this exposure. For the seed will 
germinate still, on the return of spring, when the ground has 
been again thawed, and the temperature raised to the proper 
degree. ‘This condition M. DeCandolle admits to be good, 
[V. A fourth condition necessary to germination is the ac- 
cess of moisture. Seeds will not germinate if they are kept 
* Keith, Phys. Bot., vol. ii. p. 5. + Phys. Vég., ii. 638. 
