GERMINATION. 
nate : the process itself has been called ger- 
mination. Seeds do not germinate equally 
and indifferently in all places and seasons. 
Germination, therefore, is a process which 
does not depend upon the seed alone: some- 
thing external must also affect it. 
It is a well-known fact, that seeds will not 
germinate without moisture ; for seeds, if 
they are kept perfectly dry, never vegetate 
: at all, and yet their power of vegetating is 
not destroyed. Water, then, is essential to 
germination. Too much water, however, is 
no less prejudicial to most seeds than none at 
all. The seeds of water-plants, indeed, ger- 
minate and vegetate extremely well in water ; 
I but most other seeds, if they are kept in wa- 
| ter beyond a certain time, are rotted and de- 
I stroyed altogether. 
It is well known also, that seeds will not 
germinate, even though supplied with water, 
provided the temperature is b low a certain 
degree. No seed, for instance, on which 
[ the experiment lias been tried, can be made 
| to vegetate at or below tire freezing-point : 
| yet this degree of cold does not injure the 
vegetating power of seeds; for many seeds 
will vegetate as 'well as ever after having been 
frozen, or after having been kept in frozen 
water. We may conclude, then, that a cer- 
tain degree of heat is necessary for the ger- 
mination of seeds. And every species of 
plants seems to have a degree peculiar to it- 
self, at which its seeds begin to germinate ; 
for every seed has a peculiar season at which 
it begins to germinate, and this season varies 
with the temperature of the air. Mr. Adan- 
son found that seeds, when sown at the same 
time in France and in Senegal, always ap- 
peared sooner above ground in the' latter 
country, where the climate is hotter, than in 
France. 
Seeds, although supplied with moisture, 
and placed in a proper temperature, will not 
germinate, if atmospherical air is completely 
excluded from them. Mr. Ray found that 
grains of lettuce did not germinate in the va- 
cuum of an air-pump, but they began to 
grow as soon as air was admitted to them. 
Homberg made a number of experiments on 
the same subject, which were published in 
the Memoirs of the French Academy for the 
year 1693. He found that the greater num- 
ber of seeds which lie tried refused to vege- 
tate in the vacuum of an air-pump. Some, 
however, did germinate ; but Boyle, Mus- 
chenbroek, and Boerliaave, who made expe-“ 
riments on the same subject in succession, 
proved beyond a doubt that no plant vege- 
tates in the vacuum of an air-pump ; and that 
in those cases in which Ilomberg’s seeds 
germinated, the vacuum was far from per- 
fect, a quantity of air still remaining in the re- 
ceiver. It follows, therefore, that no seed 
will germinate unless atmospherical air, or 
some air having the same properties, has ac- 
cess to it. It is for this reason that seeds will 
not germinate at a certain depth below the 
surface of the earth. 
Mr. Scheele found that beans would not 
germinate except oxygen gas was present. 
Mr. Achard afterwards proved that oxygen 
gas is absolutely necessary for the germina- 
tion of all seeds, and that no seed will germi- 
nate in azotic gas, or hydrogen gas, or carbo- 
nic acid gas, unless these gases contain a mix- 
ture of oxygen gas. These experiments 
have been confirmed by Mr. Gough, Mr. 
Cruickshank, and many other philosophers. 
It follows, therefore, that it is not the whole 
atmospheric air, but merely the oxygen gas 
which it contains, that is necessary lor the 
germination of seeds. 
Nay, M. Humboldt has ascertained that 
seeds Vegetate more rapidly when steeped in 
oxymuriatic acid, or when watered with it; 
and this acid is well known for the facility 
with which it parts with oxygen. This acid 
seems even to augment the vegetative power 
of seeds. At Vienna several seeds which had 
been long kept, and which had constantly re- 
fused to germinate, grew readily when treat- 
ed with this acid. 
Light also has considerable influence on the 
germination of seeds. Ingenhousz found that 
seeds always germinate faster in the dark than 
when exposed to the light. His experiments 
were repeated by Mr. Sennebier with equal 
success. But the abbe Bertholin, who distin- 
guished himself so much by his labours to 
demonstrate the effect of electricity on vege- 
tation, objected to the conclusions of these 
philosophers; and affirmed that the difference 
in die germination of seeds in the shade and 
in the light was owing, not to the light itself, 
but to the difference of the moisture in the 
two situations ; the moisture evaporating 
much faster from the seeds in the light than 
from those in the shade ; and he affirmed, 
that when precautions were taken to keep the 
seeds equally moist, those in the sun germi- 
nated sooner than those in the shade. But 
when Mr. S. nnebier repeated his former ex- 
periments, and employed every possible pre- 
caution to ensure the equality of moisture in 
botli situations, lie constantly found the seeds 
in the shade germinate sooner than those in 
the light. We may conclude, therefore, that 
light is injurious to germination; and hence 
one reason for covering seeds with the soil in 
which they are to grow. 
Thus we have seen that seeds will not ger- 
minate unless moisture, heat, and oxygen gas, 
are present; and that they do not germinate 
well if they are exposed to the action of 
light. Now, in what manner do these sub- 
stances affect the seed ? What are the changes 
which they produce? 
It was observed before, that all seeds have 
one or more cotyledons. 1 hese cotyledons 
contain a quantity of farinaceous matter, laid 
up on purpose to supply the embryo plant 
with food as soon as it begins to require it. 
This food, however, must undergo some pre- 
vious preparation before it can be applied by 
the plant to the formation or completion of 
its organs. Now all the phenomena of ger- 
mination, which we can perceive, consist in 
the chemical changes which are produced in 
that food, and the consequent developement 
of the organs of the plant. 
When a seed is placed in favourable cir- 
cumstances, it gradually imbibes moisture, 
and very soon after emits a quantity of car- 
bonic acid gas, even though no oxygen gas 
should be piesent. If no oxygen gas is pre- 
sent, the process stops here, and no germina- 
tion takes place. But if oxygen gas is pre- 
sent, it is gradually absorbed by the seed ; 
and at the same time the farina of the cotyle- 
dons assumes a sweet taste, resembling su- 
gar : it is therefore converted into sugar, or 
some substance analogous to it. M. Saus- 
sure, jum has ascertained that the quantity of 
oxygen gas absorbed during the germination 
6-15 
is always proportional to the carbonic acid 
gas emitted ; that is, the carbonic acid emit- 
ted contains in it precisely the same quantity 
of oxygen as has been absorbed. Hence it 
is evident that the farina is changed into su- 
gar by diminishing its carbon, and of course 
by augmenting the proportion of its hydro- 
gen and oxygen. 1 his is precisely the pro- 
cess of ma ting, or of converting grain into 
malt; during which it is well known that 
there is a considerable heat evolved ; so 
much indeed, that in certain circumstances 
grain improperly kept has even taken lire. 
We may conclude from this, that during the 
germination of seeds in the earth there is also 
an evolution of a considerable portion of 
heat. This indeed might have been expect- 
ed, as it usually happens when oxygen gas is 
absorbed. 
So far seems to be the work of chemistry 
alone, at least we have no right to conclude 
that any other agent interferes ; since hay, 
when it happens to imbibe moisture, exhibits 
nearly the same processes. Carbonic acid 
gas is evolved, oxygen gas is absorbed, heat 
is produced so abundantly that the hay often 
takes lire : at the same time a quantity of 
sugar is formed. It is owing to a partial 
change of the same kind that old hay gene- 
rally tastes much sweeter than new hay. 
Now we have no reason to suppose that any 
agents peculiar to the vegetable kingdom re- 
side in hay : as all vegetation, and all power 
of vegetating, are evidently destroyed. 
But when the farina in the seeds of ve- 
getables is converted into sugar, a number of 
vessels make their appearance in the cotyle- 
don. These vessels may indeed be detected 
in many seeds before germination com- 
mences ; but they become much more dis- 
tinct after it has made some progress. 
Branches from them have been demonstrated 
by Grew, Malpighi, and Hedwig, passing 
into the radicle, and distributed through every 
part of it. Idles e evidently carry the nou- 
rishment prepared in the cotyledons to the 
radicle; for if the cotyledons are cut. oil, 
even aft^r the processes above described are 
completed, germination, as Bonnet and Sen- 
nebier ascertained by experiment, immedi- 
ately stops. Idle food therefore is conveyed 
from the cotyledons into the radicle ; the ra- 
dicle increases in size, assumes the form of a 
root, sinks down into the earth, and soon be- 
comes capable of extracting the nomishment 
necessary for the future growth oi the plant.- 
Even at this period, after the, -radicle, lias be- 
come a perfect root, the.- plant, as Semicbier 
ascertained by experiment, ceases to vegetate 
if the cotyledons are cutoff. 1 hey are still 
then absolutely necessary tor the vegetation 
of the plant. 
The cotyledons now assume the appearance 
of leaves, and appear above the ground, 
forming what are called the seminal leaves ot 
the plant.- 1 . After this the plumula gradually 
increases in size, rises out oi the earth, and 
expands' itself into branches and leaves. 1 iie 
seminal leaves; soon after this, decay and 
drop off; and the plant carries on all the pro- 
cesses of vegetation without their assistance, 
i Mr. Eller attempted to shew that there is 
a vessel in seeds which passes irom the coty- 
ledons, to the. plumula ; but later anatomists 
have not been able to perceive any such ves- 
sel. Even Mr. Hedwig, one of the most pa- 
! tient, acute, and successful philosophers that 
