at different Degrees of Constant Temperature. 259 
Six of the species observed have no albumen, viz. the three Cru- 
ciferae, Cucumis, Trifolium, and Sesamum; the four others, Nigella, 
Linum, Collomia, and Zea Mais, have an albumen. That of maize 
is considerable ; that of lmseed, on the other hand, is very small. 
The three species which have a more or less considerable amount 
of albumen, require a minimum of 5°, and sometimes more, for 
germination. Stnapis, Lepidium, and Linum, which germinate 
at very low temperatures, have no albumen, or very little. On 
the other hand, it is a striking circumstance to find that the seeds 
of Sesamum, which greatly resemble those of the Cruciferee in 
the absence of albumen, in texture, and in size, require from 
10° to 12° to germinate. 
A temperature of 17° to 18° is favourable for all these seeds. 
At this temperature, germination took place im the following 
order :—Lepidium, Sinapis, Trifolium, Sesamum and Linum, 
Iberis, Maize, Collomia, Nigella, and Melon; which shows better 
that the albumen has a certain retarding influence. The melon, 
it is true, is the slowest, although free from albumen; but the 
coriaceous nature of its envelopes must impede development. 
7. Relation of the temperature to the time required for germination. 
All the species presented a tolerably similar progress as regards 
its duration at different temperatures. 
Near the minimum, a slight increase of temperature notably 
abridges the time of germination. Under more favourable 
means, the acceleration is slight. Lastly, near the maximum, 
the intensity of the heat becomes injurious and retards germina- 
tion. The latter is impossible at a higher degree. MM. 
Edwards and Colin had already remarked this*; and it is evi- 
dent at a glance on constructing curves expressing the results of 
my experiments (see Plate IV.). 
The Centigrade degrees being marked on the vertical line, and 
the days (of twenty-four hours) on the horizontal line, I have set 
down each observation by means of a point indicating the moment 
at which the seeds of each species germinated, at each constant 
temperature. These points are connected by straight lines, which 
indicate, with the aid of a little imagination, what the normal 
curves would be if founded upon more numerous and perfectly 
exact observations. 
It is at once evident that my observations at from 3° to 6° 
and at 17° are not very satisfactory, for they have given the 
curves an irregular form. It may also be seen that the linseed 
has presented several anomalies, perhaps arising from the some- 
what irregular rupture of the spermoderm at a certain stage of 
the evolution of the embryo. 
* Ann. d. Se. Nat. sér. 2. vol. i. p. 270. 
17% 
