102 
THE COTTAGE GARDENER. 
December 27. 
ami their experiments embraced many other seeds 
than those of the lettuce. So soon as pneumatic 
chemistry demonstrated that the atmospheric air is 
composed of several gases, viz.— 
Oxygen . 21 
Nitrogen...... 79 
100 
With about one per cent, of aqueous vapour in the 
driest weather, and about one part in every thousand 
of carbonic acid gas, the question then arose, Which 
of these gases is necessary for germination? and 
Scheele was the first to demonstrate that it is the 
oxygen. Achard afterwards proved that seeds will 
not germinate in nitrogen, carbonic acid, or hydro¬ 
gen gases, unless mixed with oxygen; and though 
Carradori doubted the correctness of his experiments, 
]iis doubt was shown to be groundless by the more 
accurate researches of Gough, Cruicksliank, Saus- 
sure, and others.* Senebier carried his experiments 
still further, and lias determined that although seeds 
will not germinate in an atmosphere not containing 
at least one-eighth of its bulk of oxygen, yet that the 
proportion most favourable to the process is about 
one-fourtli. Germination will proceed in an atmo- 
sphere of pure oxygen, but not so readily as when it 
is mixed with other gases. The same phenomena 
attend the incubation of eggs—they will not hatch 
in the vacuum of an air pump, nor will the process 
proceed satisfactorily in any other mixture of gases 
than atmospheric air. 
it is necessary that the oxygen should penetrate 
to the cotyledonous, or inner, parts of the seed, as is 
evident by the changes which take place during ger¬ 
mination ; and it is further proved by experiment. 
When healthy seed is moistened and exposed in a 
suitable temperature to atmospheric air, it absorbs 
the oxygen only. This power of separating one gas 
from the others, appears to reside in the skin of the 
seed, for old seeds loserihe power of absorbing the 
oxygen, and consequently of germinating; yet they 
will frequently germinate if soaked in a solution of 
chlorine in water—a gas which has the power of at¬ 
tracting hydrogen from water, and others of its com¬ 
pounds, and releasing the oxygen, doing so in the 
case of seeds within their skin, as well as without- 
side. Humboldt and Saussure have also shown that 
the application of chlorine to seed accelerates its 
germination, and cress seed, which, under ordinary 
circumstances, requires some days to complete the 
process, they found effected it in no more than three 
hours. The late Mr. George Sinclair, author of 
the excellent Hortus Gramineus Wobumenm, in¬ 
formed us that he employed chlorine with singular 
success. He obtained it by mixing a tablespoonful 
* Although seeds will not germinate in an atmosphere of nitrogen, 
yet they all absorb a small quantity of this gas when germinating. 
It is a constituent of most young roots, especially of their spongioles, 
or extreme points. There is reason to believe that ammonia is 
formed during germination, and that it acts as a stimulant and food 
to the young plant. Seeds containing nitrogen germinate more 
rapidly than seeds of the same genus which do not contain this gas, 
' of muriatic acid (spirit of salt) with a similar quail- 
1 tity of black oxide of manganese, and half a pint of 
: water. After allowing the mixture to remain two or 
three hours, the seed is to be immersed in the liquid 
for a similar period, and then sown. Another, and, 
we consider, the most eligible mode of applying the 
chlorine, was also suggested to us by the same dis¬ 
tinguished horticulturist. In this way he said he 
made tropical seeds vegetate, which refused to ger¬ 
minate by other modes of treatment. He placed the 
mixed ingredients mentioned above in a glass retort, 
inserting its bulb in the hot-bed, and bringing its 
beak under the pot in which the seeds were sown 
connecting it with the draining aperture of the pot. 
The chlorine gas is gradually evolved, passing 
through the earth of the pot to the seeds, accordingly 
as the heat required for the different species induces. 
This absolute necessity for the presence of oxygen 
is a reason why seeds will not germinate if buried 
beyond a certain distance from the earth’s surface ; 
and why clayey soils often fail of having a good 
plant, an impervious coat of the clay enveloping the 
! seed, and preventing the air’s access. 
M. Burger found that seeds of rye buried one inch 
below the surface had their leaves above it in eight 
days and a half, whereas those at a depth of 
six inches, had only just sprouted at the end of 
twenty-two days. But too deep sowing inflicts an¬ 
other injury; though it be not at such a depth as to 
entirely prevent germination, it so consumes the 
matter of the seed in forming the useless elongation 
of stalk necessary to bring the leaves above the sur¬ 
face, that allj'urtlier progress in vegetation has been 
prevented. M. Burger found that rye seeds, sown 
five inches and a half deep, forced their blades to 
the surface in seventeen days and a-half, but these 
remained green only for six days, and then withered; 
and that, in everyjnstance, the most sliallow-sown 
seeds produced the most stalks. I have observed the 
same in the case of kidney beans, Windsor beans, and 
peas of various varieties; those seeds buried one 
and a half inch below the surface, invariably grew 
higher, and were more prolific, than those buried at 
double or even greater depths. 
Erom Saussure’s experiments, we learn that weight 
for weight, wheat and barley during germination 
absorb less oxygen than peas, whilst these consume 
less than beans and kidney beans. This explains 
why, in proportion to their size, the two first may be 
sown at a greater depth below the soil’s surface than 
the three last named, without vegetation being pre¬ 
vented. 
It is chiefly the want of a due supply of oxygen 
that forbids seeds germinating which are buried at 
i great depths; seeds thus deposited, or similarly ex- 
| eluded from the air in the Egyptian mummy cere- 
i ments, will often retain their vegetative power for 
i apparently unlimited time. Hence, earth taken 
