714 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
•y. General. 
Luminous Plants.* — M. H. Gadeau de Kerville enumerates the 
plants in which luminosity has been observed, which he classifies under 
four heads : — (1) Fungi; (2) Bacteria; (3) Mosses (Schizostega osmun- 
dacea ); (4) Flowering plants, viz. the rhizome of some Indian grasses, 
the latex of Euphorbia phosphorea, the leaves of Phytolacca decandra , and 
many flowers. In the flowers the luminosity is not constant, but appears 
in flashes in the dark, and is probably connected with atmospheric 
electricity ; while in the fungi and bacteria it is dependent on a vital 
process going on in the protoplasm. 
Purification of Streams by Chlorophyllous Plants.t — It is a well- 
known fact, says Dr. T. Bokorny, that green plants can take up and 
assimilate organic substances, and it seems equally indubitable that 
water-bacteria have a share in the purification of water, and that bacteria 
play a very important part so long as the water contains a considerable 
quantity of organic matter. To what extent green plants share in the 
purification of streams the author determined to test by experiment. It 
had previously been shown that phanerogamic plants can use as nutri- 
ment organic substances such as sugar, glycerin, Ac. ; and the author 
chiefly occupied himself with the behaviour of Algae, especially Diato- 
maceae, as regards putrefaction products and urine. Volatile fatty acids, 
amido-acids, indol, scatol, phenylacetic acid, urea, &c., were exposed in 
suitable solutions, with free access of light, and with exclusion of light, 
to the action of Algae. The results were positive ; for Algae were found 
capable of using as nutriment volatile fatty acids, such as butyric and 
valerianic, and also glucose, leucin, and tyrosin. Even urea when 
properly diluted could be assimilated. It may therefore be upheld that 
a considerable number of organic substances which are carried into 
rivers by drains are destroyed by water plants, though it must be re- 
membered that water-bacteria are responsible for a large share of the 
work. Both co-operate, and by their united action free streams from 
dissolved organic matter. 
Spontaneous Purification of River Water.J — After alluding to the 
condition of the Seine about Paris, and the quantity of impurities 
deposited in the river from the city, M. Duclaux shows that lower down 
the river has again become practically pure. The case of the Isar, 
which flows by Munich, the condition of which was examined by 
Prausnitz, is mentioned here in detail. Prausnitz found that water 
entering Munich contained 305 germs per ccm., while 7 kilometres 
below there were 12,600. By the time the stream reached 33 kilo- 
metres from Munich, which it did in 8 hours, the number of germs had 
diminished by five-sixths. 
The causes of this purification, says the author, are both physical 
and vital. Among the physical, one principal action is that of the 
ground waters which mingle with the stream along its course. These 
influence purification partly from their lower temperature in summer 
* Weber’s Naturw. Bibliotliek, 1893, 242 pp. and 27 figs. See Bot. Centralbl., 
1894, Beih., p. 228. 
t Arch. f. Hygien., xx. (1894) No. 2. See Centralbl. f. Bakteriol. n. Parasitenk., 
xvi. (1894) pp. 91-2. % Ann. Inst. Pasteur, viii. (1894) pp. 117-27. 
