264° * M. A. de Candolle on Germination. 
of all the heat ; or, again, a temperature of 20° during ten days, 
which makes 200°, has more influence upon the development of 
the worm than a temperature of 10° during twenty days, which 
also amounts to 200°. The 200° are insufficient in the latter 
case and superabundant in the former.” 
We here see the influence of a minimum, which exists in the 
instance of the egg as also of the seed: if the silkworm requires 
9°, it is evident that a mean of 10° is of little use. 
10. Analogy of germination with combustion. 
The production of carbonic acid by means of the oxygen of the 
air has always caused germination, like respiration, to be classed 
with phenomena which may be termed generally combustion. 
For the sake of analogy, the necessity of a certain initial heat 
must also be added in the case of germination; only, in seeds the 
minimum of temperature is low : mustard-seed burns at 0°. As 
regards the more or less rapid progress of germination, the seed 
must be compared to a combustible which is acted upon slowly 
and successively within by heat. There are two envelopes, and 
frequently cellular tissue gorged with starch, surrounding the 
embryo, which must evidently retard the influence of heat, as also 
of oxygen and moisture, upon the internal organs. 
11. Peculiar nature of germination. 
At first sight, every one is inclined to regard germination as 
something extraordinary and inexplicable, 2. e. vital, in which 
heat and oxygen reanimate the young plant, which is well-known, 
however, not to be dead. I fear that this kind of consideration 
must be left to poets; for the more germination is studied, the 
more it seems to be composed of solely physical and chemical 
paenomena. 
It is true that I have not examined the modifications under- 
gone by the tissues of seeds at the different temperatures to which 
I have subjected them. This kind of research would be of 
great interest, and would require explanation by means of the 
microscope, with the same care as that used by M. Arthur Gris 
in his recent papers on the anatomy of seeds beginning to ger- 
minate. We should like to know what alterations the seeds 
undergo below their minimum of germination, above their max- 
imum, also in the intermediate degrees which favour more or less 
each partial function, of which the sum total constitutes ger- 
mination. It is true, that the external appearance indicates 
part of these phenomena. Below the minimun, seeds kept in 
a moist medium and being unable to germinate, slowly decay ; 
above 45° to 50° they begin to be carbonized. It is easy to 
