108 
m 
nus, Humuhis, Gentiana cruciatd and in the bark of Frunus, Quercus, 
etc. Threads, however, which contain no granules, but are transpar- 
ent and homogeneous, are with difficulty rendered visible. His 
method of examination is to lay the sections to be examined in a sol- 
ution of 0.2 per cent, of iodine and 1.64 per cent, of potassium iodide 
m concentrated sulphuric acid. After removal, the sections are re- 
peatedly washed and then stained with aniline blue; in some cases 
they are previously stained with picric acid. Mr. Gardiner, however, 
considers that the sulphuric acid method is unsatisfactory and that 
the method of swelling with chloro-iodide of zinc and of staining with 
picnc-Hoffman blue is in every way more advantageous, since little 
alteration of structure takes place and the staining with blue is limited 
to the protoplasm. 
Chemical Constituents of Plants— il^xx M. Ballo contributes an 
important paper on this subject to the Proceedings of the German 
Chemical Society. He thinks that oxalic acid has a much more im- 
portant function in vegetable physiology than is generally supposed, 
carbohydrates being formed from the reduction of this and other 
vegetable acids rather than by direct synthesis from carbonic acid 
and water. Tartaric acid, on the other hand, is a product either 
of the oxidation of carbohydrates or of the reduction of oxalic acid, 
as is also the glycolic acid which occurs in unripe grapes and in the 
the leaves of the wild vine. As regards all other products of oxida- 
tion, the less the amount of oxidation the more complicated is the 
product and the more closely related to the original substance; 
whde, when oxidation is carried on further, we get the original sub- 
stances by which the plant is nourished. The vegetable acids are the 
most cornmon products of oxidation in the plant. A portion of the 
oxalic acid is used in the decomposition of calcium sulphate, the rest 
as the raw material for the production of glycolic, tartaric, malic and 
succinic acids. 
F 
If fomic acid is heated with nitric acid it is oxidized into car- 
bonic acid and water, the nitric acid being reduced to nitrous oxide; 
but at the commencement of the process oxalic acid is formed, and 
the author believes that this process also takes place in nature, and 
that this is one of the reasons why nitrates are so valuable to the 
growing plant.^ In the living plant a portion of the nitrates is used 
in the production of ammonia and other substances nearly related to 
it, and another in the conversion of amide compounds into alcohol 
compounds. The greater part is reduced to the state of nitrous oxide, 
and from this nitric acid is again formed through the agency of 
oxygen and water. Hence a small quantity of nitrates can bring 
about the formation of a large quantity of oxalates. 
Electric currents exist without doubt in the living plant, and it is 
possible that in_ some cases these may be converted into chemical 
work consisting in the decomposition not merely of water but also of 
salts. The products of decomposition of these salts may cause the 
formation of metal derivatives at the negative pole, of derivatives 
with negative radicals at the positive pole. Elsewhere, these sub- 
stances may again combine with one another and the same process 
be then again repeated. Hence the comparatively small quantity of 
inorgapir salts found in olants. 
