272 
THE FLORIST AND POMOLOGIST. 
would not teach a Crusoe to prolong his existence on a barren island; but a 
knowledge of plants might enable to subsist, and a knowledge of mechanics might 
increase his comforts, or enable him to find the means of escape. We regard, 
then, with pleasure, works which tend to encourage an acquaintance with 
science, more particularly those which relate to the delightful study of plants, 
and such a work is the “ Vegetable World.” It forms an elegant volume of 
576 large octavo pages, and is illustrated with no less than 446 engravings and 
24 plates, all of which are most beautifully executed, chiefly from drawings made 
from nature by M. Faguet, Botanical Illustrator to the Faculty of Sciences of 
Paris. It is divided into three parts, namely—1st, the Organography and 
Physiology of Plants ; 2nd, the Classification and Natural Families of Plants ; 
and 3rd, the Geographical Distribution of Plants. 
In the first division, occupying altogether 192 pages, the various parts of 
plants and their principal modifications are described in plain language, but 
with scientific accuracy, and the descriptions are made still more clear by 
numerous beautiful engravings. The functions of the various organs are also 
entered into at considerable length; and exhalation, respiration, circulation, 
fecundation, and germination are well explained. 
The following extract relative to respiration will serve as an example of the 
manner in which the author treats his subject:— 
“ If we place an entire plant or a leafy branch in a balloon filled with gas which cannot 
be renewed, and leave the whole in darkness for some ten or fifteen hours, we may assure 
ourselves at the expiration of this time that the atmospheric air contained in the balloon is 
no longer of the same composition as before the experiment. Carbonic acid will be there in 
greater abundance, and the quantity of oxygen will be less. But if in place of leaving the 
plant in darkness we expose the apparatus to the influence of the sun’s rays, the phenomena 
will be reversed; after a few hours the air in the balloon will have lost a noticeable quantity 
of its carbonic acid, and will be enriched in its oxygen. 
“ In order to test this phenomenon, let us fill a bell-glass with water, to which has been 
previously added a considerable proportion of carbonic acid gas, and place in it a branch or 
an entire plant covered with leaves; expose the whole to the rays of the sun for some hours. 
The air, if analysed after the experiment, will be found to contain scarcely any carbonic 
acid, but it will contain a larger portion of oxygen than before the experiment. If a branch 
of a plant, with the roots fixed in soil, and consequently in its normal state of vegetation, is 
placed in a glass vessel, and by means of an air-pump a given quantity of air is caused to 
circulate round it, this air, which, before the experiment, contained from four to five ten- 
thousandth parts of carbonic acid, after the apparatus has been exposed to the influence of the 
sun’s rays for a certain time will not be found to contain more than from one to two. If, on 
the contrary, the experiment is made during the night, it will be found that the quantity of 
carbonic acid would be increased, and at the expiration ef a certain time would have risen 
to eight ten-thousandth part3. These experiments, in which there is an interchange of gas 
between the plant and the atmosphere, exhibit the double phenomena of absorption and 
exhalation in plants; in fact there is respiration. But the respiration of plants is not 
always the same, like that of animals, in which carbonic acid gas, water, and vapour are 
exhaled without cessation either by day or night. Plants possess two modes of respiration : 
one diurnal, in which the leaves absorb the carbonic acid of the air, decompose this gas, and 
extract the oxygen, whilst the carbon remains in their tissues; the other nocturnal, and the 
reverse, in which the plant absorbs the oxygen and extracts the carbonic acid—that is to say, 
they breathe in the same manner as animals do. The carbon which is used by plants 
during the day is indispensable to the perfect development of their organs and the consolida¬ 
tion of their tissues. By respiration plants live and grow. 
“It is necessary to remark here that it is only the green parts of vegetables which 
respire in the manner described—that is to say, by absorbing carbonic acid and disengaging 
oxygen under the influence of light. The parts not coloured green, such as the fruit, 
seeds, red and yellow leaves, &c., always respire in one and the same manner: whether 
exposed to light or left in darkness, they always absorb the oxygen and disengage carbonic 
acid. They respire in the same manner as animals. If we consider that the green parts of 
the plant are far more numerous than those which are otherwise coloured, that the clear 
light nights of hot countries may rather be said to diminish than to interrupt their respira¬ 
tion,—that the season of long days in northern countries is that of the greatest vegetative 
activity—we shall be led to the conclusion, that the great mass of plants live more in light 
