594 SUMMARY OF CURRENT RESEARCHES RELATING TO 
In cloudy weather both processes are weakened, but transmission less so 
than assimilation. 
Formation and Decomposition of Organic Acids.* * * § — According to 
investigations carried on in flowering plants by M. K. Purjewicz, the 
decomposition of organic acids is always taking place in plants, but is 
especially favoured by (1) the influence of light, (2) the influence of a 
high temperature, (3) continuous exposure to darkness at the ordinary 
temperature. The decomposition under the influence of light takes 
place also in etiolated organs. It is accompanied by oxidation. The 
decomposition by a high temperature in the dark appears to be a 
widely spread phenomenon. 
A production of organic acids takes place in all plants in the dark 
when the temperature is not too high ; but is dependent on the previous 
formation of carbohydrates in the light. The optimum temperature lies 
between 12° and 15° C. Their formation is the result of an incomplete 
oxidation of carbohydrates ; their destruction depends on a further oxida- 
tion with production of carbon dioxide. 
^he acid formed in the Crassulaceae is malic, in Oxalis and Pelargo- 
nium oxalic, in Pobinia tartaric and citric acids. Malic acid is the most 
easily decomposed by a strong light and high temperature, then oxalic 
and tartaric acids, while citric acid is the most stable. 
Intramolecular Respiration dependent upon Carbohydrates-t — 
M. W. Palladine confirms the observations of Diakonow J (on fungi) 
that carbon dioxide is disengaged from the living cell into an atmosphere 
destitute of oxygen ; while in the case of etiolated leaves, which contain 
no carbohydrates, the quantity of carbon dioxide evolved is scarcely 
perceptible. The introduction of glucose into the tissues increases 
considerably the amount of carbon dioxide disengaged. 
Influence of Oxygen on Alcoholic Fermentation.§ — From a series 
of experiments made on pure beer-yeast, M. D. Iwanowskij has come to 
the conclusion that oxygen has no influence on the energy of fermenta- 
tion. The diminution in the energy of the process from the access of 
free oxygen recorded by other observers he believes to be only apparent. 
B. CBYPTOGAMIA. 
Cryptogamia Vascularia. 
Megaspore and Female Prothallium of Selaginella.|] — Herr E. 
Heinsen has followed out the development of the megaspore and of the 
female prothallium in various species of Selaginella. His results differ 
in some respects from those of Pfeffer, and establish a closer analogy 
with the corresponding processes in Isoetes and the Coniferse. 
The megaspore is formed endogenously in the protoplasm of the 
special mother-cell. The protoplasm within the spore is at first homo- 
* ‘ Die Bildung u. Zersetzung cl. organ. S'auren b. d. hoheren Pflanzen 1 
(Russian^, Kiew, 1893, 90 pp. and 1 pi. See Bot. Centralbl., lviii. (1894) p. 368. 
f Rev. Gen. de Bot., vi. (1894) pp. 201-9. Of. this Journal, ante, p. 371. 
j Of. this Journal, 1886, p. 835. 
§ Arb. Bot. Lab. Akad. St. Petersburg, 1893, 28 pp. See Bot. Centralbl., lviii. 
(1894) p. 344. |1 Flora, lxxviii. (1894) pp. 466-96 (1 pi. and 1 fig.). 
