76 Chronicles of Science. | Jan., 
posing organic matter, leaves, &c., which in the processes of agricul- 
ture and by the influence of the earth-worm, &c., become embedded 
in the soil. M. Corenwinder, however, does not say what becomes of 
this carbonic acid. Liebig and other chemists answer the question 
better in showing that the carbonic acid is taken up by water which 
percolates through the soil, and that it is then used in eroding rocks 
and dissolving up otherwise insoluble mineral matters. 
Aériferous Vesicles of the Utricularie.—S. B. Schnetzler pub- 
lishes an account in the ‘Annals of Natural History, of these curious 
appendages to the leaves. The genus Utricularia consists of aquatic 
plants which are found in the stagnant waters of ditches, marshes, &e. 
The leaves are submerged and divided into fine lacinz furnished with 
the remarkable utricles. De Candolle states that when the plant 
is young these vesicles are filled with a mucilage which is heavier 
than water, and the plant held down by this ballast remains at the 
bottom. Towards the period of flowering, the leaves secrete a gas 
which makes its way into the utricles and drives out the mucilage 
by raising an operculum or lid with which the utricles are furnished. 
The plant thus becomes furnished with a multitude of air-bladders, 
and rises slowly and at last floats at the surface. After flowering 
in the air, the mucilage is again secreted and the plant sinks again 
to ripen its seeds below water. M. Schnetzler has carefully inves- 
tigated the morphology and history of these organs, and concludes 
that they play the part at once of organs of respiration and of a 
hydrostatic apparatus. The organs do not appear at a given mo- 
ment and for a particular purpose, but as a natural consequence of 
the anatomical structure of the plant and the action of the sur- 
rounding medium. After some philosophical generalizations the 
author observes, “The totality of the forms in which life manifests 
itself upon the earth, during a given epoch, appears to us like a 
magnificent mosaic, of which the different pieces brought together 
mutually determine their nature.” 
The Fall of Leaves—Dr. Maxwell Masters has recently dis- 
cussed this subject in a very seasonable article in the ‘ Popular 
Science Review.’ It appears from the researches of M. Trécul 
(published in the ‘Comptes Rendus’) and others, that in many 
plants a phenomenon occurs just before the fall of the leaf, which 
is not unlike the process which accompanies the shedding of horns 
in animals. It consists in the obstruction of the proper vessels at 
the base of the petiole or leaf-stalk. This obstruction is caused by 
the multiplication of cells, which first occurs in the parietes of the 
vessels. The cells increase and multiply, till at last the vessels are 
completely choked up in the neighbourhood of the insertion of the 
leaf, and thus a differentiated plane is formed, across which the leaf- 
stalk breaks, and the leaf accordingly falls. 
Movements of the Sensitive Plant—M. Bert and M. de Blon- 
