202 
POPULAR SCIENCE REYIEW. 
they become more irregular. The lower epidermis is formed of cells of a 
very irregular outline, and, in certain species, bears stomata of an elliptical 
form. Bundles of raphides are present in large numbers, and give the leaf 
a sort of rough or rugose character. They consist of concretions of silica, 
and are unaffected by any acid save hydrofluoric. They are well seen in 
the leaf of Curatilla Americana , of which M. Baillon gives a minute 
account. Vide Comptes Rendus, February 18. 
The Nature of Sap-currents. — Herr Reichert has published an essay on 
this subject, and he states his opinions in a series of conclusions. Of these 
latter, the first three relate to the constitution of the sap-fluid. Herr 
Reichert says, that in all cells containing fluids which rotate, two distinct 
portions are present within the cellulose wall, viz., the central cell-fluid 
which occupies the axis, and the mantle layer which exists between the 
central cell-fluid and the cellulose capsule. The cell-fluid is generally 
transparent ( Tradescantia Virginica being an exception) ; its chemical con- 
stitution is not clearly understood, and it is the portion of the cell-contents 
which does not participate in the rotation. The mantle-layer consists of 
the gelatinous protoplasm, chlorophyll corpuscles, other smaller particles, the 
cell-nucleus, and certain microscopic crystals. 
CHEMISTRY. 
New Test for Cobalt in Solution. — Mr. William Skey, Analyst to the Geo- 
logical Survey of New Zealand, has communicated to a late No. of the 
Chemical News a new test for the presence of cobalt in solution. If, he says, 
ammonia in excess be added to a solution of cobalt in tartaric acid, then an 
addition of ferricyanide of potassium produces a very dark-red coloration. 
So intense is the colour thus produced by the ferricyanide, that it will 
reveal the presence of cobalt in solution when all other tests fail, its 
delicacy being about four times greater than that of carbonate of ammonia. 
A solution of cobalt, prepared as indicated above, so as only to contain 
part of cobalt, when placed in a f-inch test-tube, is very distinctly 
coloured by the addition of a soluble ferricyanide, and even when diluted 
down so as to contain but one part of cobalt in 400,000 parts of the liquid,, 
the coloration is still distinctly visible in a bulk of a few ounces. 
Action of Bismuth on Phosphoric Acid. — In the Zeitschrift fur Chetnie 7 
M. Brown states the effects of bismuth on phosphoric acid as very re- 
markable. When a fragment of bismuth is thrown into u glacial phos- 
phoric acid infusion ” the metal fuses to a bright globule, from which small 
flames are emitted. This phenomenon is sometimes so strong that particles 
of incandescent bismuth are thrown out of the vessel, forming a shower of 
sparks. There finally remains a spongy mass of bismuth, and a white 
powder, which is phosphate of bismuth. The flames which appear arise 
evidently from the phosphide of bismuth which would be formed, and 
which decomposes by giving up its phosphorus, or by forming phosphuretted 
hydrogen in contact with the water of constitution of the phosphoric 
hydrate. — Chemical News. 
