47 
lish them here in order to explain to observers the defects of ar 
experimental process to which, in the future, they would themselves 
have been tempted to resort; this, moreover, seems to me the more 
useful in that up to this time this danger does not seem to have struck 
the attention of botanists. On the other hand, my observations con- 
tain some new data relative to the temperatures favorable for the 
germination of certain exotic seeds. 
In consequence of the conclusions to which we have thus been led, 
it would be useless to study the action of the different portions of the 
solar spectrum on the apparent progress of germination. How, in 
fact, can we suppose, in view of the contradic tory results already 
obtained for the condition of light and of darkness—that is to say, 
for the most extreme conditions—that the employment of the same 
inethod can reveal a difference of action for the various portions of 
the spectrum ? 
Is it then necessary, after this first fruitless attempt, to give up the 
solution of the problem, or shall we seek it by another ‘and better 
method? It is this latter alternative that I have adopted in that I 
have taken for the basis of a new series of observtions the variations 
of a physiological process that, in an almost mathematical manner, 
measures the germinal activity of the vegetable embryo, namely, the 
respiration. 
After giving the details of his experiments on respiration of plants, 
Pauchon draws the following conclusions (p. 166) : 
The laws PEeueht prominently forward by the results of these 
experiments are 
(1) Light exercises a constant and more or less marked accelerat- 
ing influence upon the absorption of oxygen by seeds in the process of 
germination. All the experiments made in a strong light have not, 
however, the same value in demonstrating this fact.’ But if we have 
doubts about the precision of the results furnished by experiments 
in which germination did not invariably take place (and we believe 
that we have shown by some preparatory experiments that these 
results have at least a relative value), this certainly is not the case 
with experiments Nos. 2 and 8, in which all the seeds did germinate. 
Thus experiment No. 2 showed in favor of light a result as to the 
oxygen absorbed twice as great as that given by the seeds placed in 
the dark. In the same way in experiment No. 8 this superiority 
reaches to one-third of the quantity of oxygen absorbed by the seeds 
placed in the dark. Finally, the other experiments, and particularly 
those classed under Nos. 3, 6, and 7, further confirm the generality of 
this action of light, which we will, besides, find again in a second 
series of experiments reported hereafter, several of which have shown 
ay Te, of germination in both cases. 
(2) There exists a relation between the degree of light and the 
quantity of oxygen absorbed. Thus, in a diffuse light this accelerat- 
ing influence shows itself in a most marked manner when the sky 
is very clear, and the solar radiation reaches us in its greatest inten- 
sity. Such was the case in experiments Nos. 2 and 8. Whenever the 
sky is cloudy this action is more and more weakened and ceases 
altogether when the sun is completely veiled, as in stormy weather, 
so that there is a semiobscurity. 
