446 4 BOTANICAL GAZETTE [ DECEMBER 
Stahl regards nyctitropic and other related leaf movements to be most inti- 
mately connected with the process of transpiration or, in other words, the con- 
duction of solutions from the soil. This view is supported by a large number 
of facts that are admirably brought into harmonious relationship with each 
other. True nyctitropic movements are believed to facilitate nocturnal trans- 
piration ; in accordance with this view Stahl finds that the stomata of these 
plants are open at night, and that the leaves, on account of their vertical 
position, are much less strongly bedewed than are ordinary horizontal leaves. 
ence of dew, of course, facilitates transpiration, and the loss of 
water is still further favored by the fact that the leaf surface most fully 
provided with stomata is best concealed from the dew. 
Some of the tropical plants, especially legumes, assume sm: vertical or 
profile position in strong sunlight. In such cases the undoubt 
edly to reduce the transpiration, since the danger here is from too great, not 
too little loss of water. The autonomous movements of Desmodium gyrans, 
which have been hitherto unexplained, are thought to be for the purpose of 
promoting transpiration, since the movements cause the saturated air to be 
driven off, thus allowing dry air to come in contact with the transpiring sur- 
face. The quaking aspen and other poplars may secure the same results 
means of the passive movements of their leaves. 
Stahl thus associates all variation in leaf movements in one way or another 
with transpiration, and the predominantly tropical distribution of plants that 
show such movements is a strong point in favor of this view. It is a striking 
fact that the Leguminosz furnish the larger proportion of plants, and Stahl 
hints that as they have worked out such delicate apparatus to regulate the 
transpiration, a condition resulting, perhaps, ina more uncertain food supply, 
so the strange rhizobium symbiosis, characteristic of the family, may have 
been assumed to supply the deficit of nitrogen.—H. C. C 
KOHL HAS BEEN Carrying on studies in order to ascertain the photosyntactic 
energy of light of various colors. Engelmann’s observations showed that 
the energy of absorption is a mark of the energy of photosyntax. Kohi 
accepts these results and conducts experiments on alge placed in darkened 
ibers covered with colored glasses. He finds that red light permits about 
50 > per cent. of the photosyntax of white light, blue light nearly as much 
green light about 25 per cent., yellow light 12 per cent., and violet still less. 
The results from blue light are surprisingly large, and are hard to interpret 
in connection with Sachs’ well-known experiments.—H. C. C. 
Dr. A. J. Ewart’s paper* on the evolution of oxygen eon colored bac: 
teria details some interesting results. He finds that a considerable number 
73 Ber. der deutsch. bot. Ges. 15: 361-366. 1897. ‘ 
Jour. Linnean Society 33 : 123. 
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