264 Miscellaneous. 
The author sums up his results as follows :—The air of the swim- 
ming-bladder presents a composition which may vary more or less, 
relatively to the proportion of oxygen, under the following cireum- 
stances :-— 
1. The oxygen diminishes and disappears in asphyxia and other 
morbid conditions. 
2. In the fishes with an open, as in those with a closed swimming- 
bladder, the air is renewed without being derived from the atmo- 
sphere, and the rapidity of this renewal is proportional to the vigour 
of the fish. 
3. The new air presents an amount of oxygen far superior to the 
proportion of that gas usually contained in the air of the swimming- 
bladder, and also far superior to that contained in the air dissolved 
in the water.—Comptes Rendus, Nov. 16, 1863, p. 816. 
On the Intercellular Substance and the Milk-Vessels in the Root of 
the common Dandelion. By Dr. August VoGu. 
The root of the common Dandelion possesses a central woody body, 
surrounded by a thick, fleshy, strongly milky rind. If fine sections 
of the root be treated under the microscope with various chemical 
reagents, it appears that the intercellular substance occurring in the 
root consists chiefly of pectose—the same substance which occurs in 
unripe fruits and in turnips and carrots. By this it is shown that 
this substance is by no means a secretion, but a product of conver-— 
sion of the cellulose of the cell-membranes. This conversion is che- 
mical in its nature, and proceeds from without inwards. The pro- 
duction of the milk-vessels in the root of the Dandelion stands in 
connexion with this pectinic metamorphosis. ~The milk-vyessels 
which occur in this plant are perhaps among the most ramified 
which occur anywhere in plants. They form main stems, which, 
united into bundles, pass through the bark in a direction parallel to 
the axis of the root. These main stems throw out a quantity of 
lateral shoots—sometimes as short transverse branches of intercom- 
munication, sometimes as czecal branches of greater or less length, 
which are either inflated into a knob or drawn out to a hair-like 
fineness at the extremity; the different bundles are connected in a 
tangential direction, and thus form large reticulated systems around 
the woody nucleus. On examining into their origin, it appears that 
their main stems are produced by the amalgamation of the so-called 
conducting cells (Leitzellen, Siebzellen) which accompany the bundles 
of milk-vessels, and probably constitute the organ for conducting 
back the juices elaborated in the leaves. This fusion is induced by 
the conversion into pectose of the membranes of the cells, consisting 
at first more or less entirely of cellulose.—Bericht der kais. Akad. 
der Wissenschaften in Wien; Math.-naturw. Classe, Dec. 17, 1863, 
p- 10. 
