ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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axial growing on a foliar structure, and so furnish further evidence of 
the homology of leaf and stem. 
Photographic Demonstration of the Function of Chlorophyll in the 
living Plant.* — M. C. Timiriazeff has demonstrated the concurrence of 
the absorption-spectrum of chlorophyll and its physiological function 
by the following experiment. A leaf still attached to a plant which 
had been kept in the dark for two or three days, was exposed, in a dark 
chamber, to a well-defined spectrum, obtained by means of a Silberman 
heliostat, from an achromatic lens and a direct-vision prism. The in- 
visible image produced by the deposit of starch is developed by means of 
a rapid decoloration of the leaf by boiling alcohol and subsequent treat- 
ment with tincture of iodine. By this process there is produced on the 
pale-yellow ground of the leaf the image of the spectrum of chlorophyll 
as if traced by Indian ink. The spectrum which registers in the living 
leaf the production of starch, corresponds in all respects to the curve 
which represents the intensity of the decomposition of carbon dioxide 
obtained by the method of gazometric analysis. 
Assimilation of Mineral Salts by Green Plants.f — Herr A. F. W. 
Schimper publishes the results of detailed observation on the part played 
by mineral salts in the economy of the plant. Immediately on germi- 
nation the phosphates begin to leave the seed; in conjunction with 
organic substances their ultimate goal is the growing point and the 
mesophyll of the leaves. The mineral acids pass through the long- 
celled parenchyme of the stem and veins of the leaf containing but little 
chlorophyll, through which sugar and the amides also pass. Halopdiytes, 
and woody plants related to them but not themselves halophytes, have a 
great tendency to store up chlorides, especially in the leaves. 
Inorganic salts are never found in the primary meristem, the sieve- 
portions of the vascular bundles, the laticiferous tubes, the reservoirs 
for secretions, the pollen-grains, or the ovules ; in the mesophyll of the 
leaf and the aquiferous tissue they usually occur only in small quantities* 
the mineral bases having been assimilated, i. e. having entered into 
organic combinations. The potassium passes out of the seeds in tho 
form of potassium phosphate ; the activity of the meristem is connected 
with the formation of nuclein, nuclein being a compound of phosphoric 
acid. The leaves of the vine, and probably also of other plants, contain, 
in addition to calcium oxalate, considerable quantities of calcium tartrate 
and malate. 
The most important processes in metastasis, the synthesis of the 
carbohydrates, albuminoids, and nuclein, and the formation of proto- 
plasmic substances, can take place without the presence of calcium, but 
require considerable quantities of potassium and magnesium. Lime 
compounds are not necessary constituents of protoplasm, nor are they 
necessary for the formation of new organs, nor in the process of assimi- 
lation ; the indispensability of lime for the life of the plant depends on 
the part which it takes in processes which take place in the growing 
region outside the primary meristem, but not connected with assimi- 
lation. 
* Comptes Kendus, cx. (1890) pp. 1316-7. f Flora, lxxiii. (1890) pp. 207-61, 
