258 M. A. de Candolle on Germination 
maximum beyond which it is impossible, we find differences be- 
tween one species and another. Thus Collomia and Nigella have 
23° of amplitude, maize 26° or 27°, the melon 24° or 25°, Sesamum 
about 30°, and Sinapis nearly 40°. The maximum being varia- 
ble according to the moisture, no great value can be attached to 
these numbers. A short amplitude is evidently unfavourable to 
the geographical extension and cultivation of a species. 
5. Differences between seeds of the same species and origin. 
Sometimes natural philosophers reproach naturalists with neg- 
lecting the experimental method and constantly following that 
of observation. Here we have an instance justifying naturalists. 
Nothing is easier to submit to experiment than seeds; nothing 
appears more homogeneous, more comparable, in the same species. 
And yet seeds derived an the same source, preserved in the 
same way, and sown together, germinate in succession*. The 
fact 1s of common occurrence ; I have met with it many times in 
my experiments. Agriculturists are well acquainted with it. 
In some families, for instance the Leguminose, it occurs, as 
already stated, to a very inconvenient extent. It is because seeds 
from the same crop, the same plant, the same capsule, are not 
identical either physically or chemically. Their organization is 
very complicated, as is also their evolution, although other 
physiological facts are still more so. Natural philosophers reason 
upon homogeneous bodies; naturalists upon heterogeneous bodies. 
A metal melts at a constant temperature, because it is composed 
of similar parts. An organized body never presents this complete 
similitude of all the parts of the same organ. Hence there is less 
exactness in the experiments, and almost constant necessity of 
comparing numerous facts, 2. e. of observing. 
In my experiments, one, two, or several “seeds have been ob- 
served germinating in succession, out of ten or twenty; and I 
have called germination, somewhat arbitrar ily, the second or third 
appearance of the radicle among the seeds. If the temperature 
is very favourable, that of several seeds takes place simultaneously. 
Near the maximum and, especially, the minimum, the seeds germi- 
nate more irregularly, and a still larger number do not germinate, 
6. Influence of the albumen. 
The structure of each kind of seed, especially the absence or 
presence of albumen, and its nature ahs it exists, must exert 
a certain infiuence in accelerating or retarding the action of heat; 
but the small number of species upon which I experimented 
has not allowed me to determine this point sufficiently. 
* See Cohn, ‘Symbola ad Seminis physiologiam,’ 8vo, Berlin, 1847. 
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