JWiscellanies. 363 
ed with ajerk, and equally so if it be strong enough to bear five kilo- 
grammes, although in that case, it is stronger than the other. This re- 
sult is explicable on the principle of the inertia of the weight B.— Idem. 
- 
i 
19. Respiration of Plants—The opinion of some physiologists, 
that leaves are the luags of plants, has been revived by Brongniart, 
whose fesearches into the anatomical structure of leaves have dem- 
onstrated, in these organs, the existence of a great number of aerial 
cavities, situated especially on the inferior surface of the leaf, and 
communicating with the external air by the openings of the stomas. 
He did not however prove that this enclosed air exerted a physiolo- 
gical effect, analogous to the air employed in the respiration of ani- 
mals. M. Durrocuer, ina lecture before the Academy, on the 
11th of July, states, that having observed that certain leaves, and 
principally those of the leguminose, speedily lost the white tint of their 
lower surface, when plunged into water, suspected that it was occa- 
sioned by imbibition of the fluid into the little aerial cavities. This 
opinion was confirmed by an experiment, the particulars of which 
were detailed in his lecture. He has proved that the aerial cavities 
of leaves are. not isolated, but form part of a pneumatic system, 
which extend continuously throughout the plants. ‘These aerial or- 
gans are filled with a gas composed of oxygen and azote, in variable 
proportions, but of which the oxygen is always in less proportion than 
in atmospheric air; proving that it has been absorbed by the plant. 
He further shews by experiment that this internal air is indispensably 
necessary to the vitality of the plant. Plants breathe, therefore, ex- 
actly like insects; that is to say, by a transfer of respirable elastic 
air, through all their parts. But the origin of this respirable air is 
not exactly the same: insects draw all their respirable air from the 
atmosphere which surrounds them ; vegetables derive from it only 
a portion of theirs; they elaborate a greater portion in tissues by the 
influengg of light, so that they can be suffocated both by the air 
pump and by darkness.—Rev. Encyc. July, 1831. 
20. Cultivation of the material used in the fabrication of Leghorn 
hats—The Royal Chamber of Agriculture and Commerce, at Nice, - 
published in 1830-31 two small works containing elementary in- 
structions relative to some points in the agriculture of that vicinity. 
Among them is the following notice of the grain which produces the 
material of Leghorn hats. 
