THE CULTIVATOR. 
261 
tion, was two hundred and fifty rotations in a minute, a 
new force came into operation—the centrifugal force— 
and overcame that of gravitation. The roots, instead of 
descending, obeyed this new force, growing outwards, 
forming in fact, prolongations of the radii of the wheel; 
while the stems took the opposite direction, until they 
came in contact with the axis. But when the wheel 
revolved less rapidly, so that the force of gravitation 
was not overcome but merely modified, the radicles point¬ 
ed downwards, about ten degrees from the horizon, and 
the plumules pointed upwards at the same angle, and the 
inclination was greater or less, according as the wheel 
revolved more or less rapidly. By this capital experi¬ 
ment, Mr. Knight proved that the descent of the roots 
into the soil, is essentially connected with gravitation. 
Botanists then considered that the lateral branches were 
due to the same cause; their natural tendency being to 
proceed upwards, but gravitation pulling them down¬ 
wards. To a certain degree only, is this correct. Par¬ 
asites do not obey the law of the earth’s attraction; for 
they always grow at right angles to the plant to which 
they are attached, whether that be upwards, downwards, 
or laterally. Now, branches given off from the stem 
may be considered parasites, which would grow at right 
angles from the stem horizontally; but they were also 
influenced by the upward direction, so that they grow 
upwards and outwards, and to a certain extent also by 
attraction, so that their direction is varied. The direc 
tions of the stem and leaves, in fact all the green parts, 
are much influenced by light, which is therefore one 
great cause of their upward direction, as shown even in 
the case of a root; when its tip becomes green it grows 
upwards like a branch; and a stem, put under the ground 
away from light, grows downwards like a root. Similar 
love for light is seen in the leaf; the upper part of a leaf 
is deeper green than the lower surface, and bends up¬ 
wards to the sky; while the latter is directed to the earth 
In some cases, both the upper and under surfaces of the 
leaf are equally green, and then its edges point to the 
sky. This was strikingly seen in the plant called bent 
grass. It had its rough or unpolished side upwards, and 
its beautiful smooth green side downwards, and it twist 
ed up its leaves to the sun so that the polished side 
should turn upwards to the light. 
The first point in the growth of plants is the germina¬ 
tion of the seed, the cotyledon of which contains a stored- 
up nutriment for the embryo—consisting of some mine¬ 
ral matter, w r ith starch, gum, cheese, and fatty oils; 
although in some seeds, as in the anise and cummin, the 
fixed fat is substituted by a volatile oil. The analysis of 
Boussingault gave 27 per cent, of cheese in peas; his 
(Dr. Playfair’s) own gave 29 per cent.; the two varie¬ 
ties obviously differing. The analysis of the French 
chemists gave 10 per cent, of this cheesing matter in oats; 
those made by the lecturer himself, yield between 11 
and 12 per cent. The oily matters also vary: some seeds, 
as that of the colewort, contain 40 per cent of oil; while 
that of wheat does not contain one per cent. It would 
be seen then, that in order that a seed should germinate, 
the concurrence of a proper temperature of moisture and 
of air was absolutely essential. Formerly, physiologists 
believed that light was injurious to germination; this 
error originating in the fact, that seeds germinate best at 
a certain distance beneath the surface of the ground. 
But Saussure showed that the apparently injurious effect 
of light was owing to the drying of the seed when too 
near the surface. He took two seeds, placed one of them 
in an opaque, the other in a transparent glass; watering 
them both alike; and he found that the seeds in the 
transparent glass germinated first. When seeds are 
placed under a jar of air, and properly supplied with 
water, the radicles and the stem soon appear. Supposing 
that there is no alteration in temperature or in conditions, 
Saussure, in his first experiments, found that the bulk of 
the air remained unchanged, although a quantity of the 
oxygen had been abstracted, and replaced by carbonic 
acid. This led Saussure to believe, that the first act of 
germination was simply the extraction of carbon by 
means of oxygen. Oxygen is quite essential to germi¬ 
nation, which cannot be made to take place in any gas 
not mixed with this element. But what is very curious, j 
carbonic acid gas, which is the primary food of plants 
is positively injurious to germination. In fact, germi¬ 
nation proceeds more rapidly, if fragments of lime are 
placed along with the seeds to absorb the carbonic acid. 
Saussure was not quite correct in his first experiments; 
for, on inspecting them with minute accuracy, he found 
that some plants actually did increase the bulk of the air, 
while others diminished the bulk. To Boussingault 
belongs the honor of having explained this phenomena. 
That distinguished philosopher, during the last year, 
had made some excellent experiments on germination. 
He analysed some seeds before germimation, and set 
others to germinate. When the plumule and radicle be¬ 
gan to appear, he analysed them again, and so on until 
the stems and the leaves were distinctly formed. The 
results of his experiments were, as Saussure had per¬ 
ceived, that there is a quantity of carbon abstracted by 
oxygen; but the loss of weight is greater than can be 
accounted for by the carbon removed. Some of the 
oxygen in the seed has also disappeared, so that it was 
obvious that part of the carbon had become burned at 
the expense of the oxygen existing in the seed itself; 
and this circumstance completely accounts for the altera¬ 
tion in the volume of air observed by Saussure. But, 
after all, this is only the ultimate view of the process; 
for there can be little doubt, that the operations in pro¬ 
gress are much more complex than the immediate ex¬ 
traction of carbon. If seeds in the act of germination be 
put upon blue litmus paper, the blue color becomes 
j changed into a red, showing distinctly that an acid is 
produced during the act. Becquenel thought this was 
acetic acid; but Boussingault suggests with much more 
plausibility, that it is the acid obtained from milk—the 
lactic acid. Be that as it may, the formation of the acid 
indicates that there are intermediate steps in germination; 
respecting which the chemist is entirely ignorant. When 
the seeds are examined after the first act of germination, 
the process is very difficult to follow. The act of ger¬ 
mination still progresses; but the act of vegetation does 
so too, and both are in antagonism. Germination ab¬ 
stracts carbon from the seed; vegetation adds carbon by 
drawing it from the atmosphere, in the form of carbonic 
acid. One thing, however, is certain, from Boussin- 
gault’s analysis, that ammonia now disappears from the 
seed. These were merely indications how to proceed 
in our investigations, in order to develope this most 
interesting act of passive into active life. At present our 
information might be considered almost nil; but the 
recent researches are full of hope; and if carried on 
with the united care of the physiologists and the chemist, 
will doubtless lead us nearer to truth. The uncertainty 
as to the nutrition of the embryo, ends with the develop¬ 
ment of the leaves; the young plant has been ushered 
into being, and we can now clearly follow its course to 
maturity. In conclusion, he would draw attention to 
this singular first act of life. The physical function of 
animals was to expire carbonic acid; that of plants to 
expire oxygen. But the first act of the embryo was 
to assume this high function of animals. Reason on 
this as we might, there was some curious mystery to 
develope in the extraordinary relations of life. The 
first act of vegetable existence was one possessed by the 
most elevated of animals; but then again it assimilated 
itself to similar functions in the lowest order of vegeta¬ 
bles. The fungi do the same; they do not live on the 
air, but on decaying substances, and breathe out carbonic 
acid. Was the first act of vegetation a lofty or low act 
of life ? If the,exhalation of oxygen from plants were 
one of the most important purposes of their life (as it 
doubtless was,) how came it that the lowest order of ani¬ 
mals, the animalcules, also possess this function ? These 
were strange anomalies, which however inexplicable at 
present, philosophers should not relax in their endeavors 
to penetrate. In fact, as he proceeded he thought he 
should be able to trace out, in this apparent contradic¬ 
tion, the most beautiful harmony and most exquisite de 
sign of means to end—a harmony and design which 
make us only the more regret that our own ignorance 
and want of power prevent us giving to them at present 
a more intimate comprehension. 
