1908] CURRENT LITERATURE 73 
mesophyll cells from excessive light, and made exact measurements as to the 
efficiency of some of them. Light from a lamp, concentrated by a reflector, was 
allowed to fall upon the experimental leaves at an angle of 45° in a suitable moist 
chamber, and the differences measured by means of a thermocouple of needle 
form, inserted between two pieces of the leaf, and connected with a galvanometer. 
The cooling by evaporation as a source of error during the exposure (10-15 
min.) could not be wholly avoided, but was assumed to be nearly uniform in the 
control and the experimental leaves. 
The results show that hairy, scaly, shining, and glaucous leaves become less 
heated than the same leaves deprived of protection. A thick white coating of 
hairs, as in Centaurea candidissima, reduces the heating effect 37.5 per cent., 
shininess up to 30 per cent., and wax coating up to 13.6 per cent. A layer of water 
reduces it 19.2 per cent.; but this result seems more open to objection on the score 
of cooling by evaporation than the others, though the author takes it to be as 
valid as the rest. Reflection is held to be due in some Bromeliaceae to the inner 
epidermal wall, the cell acting like a concave lens, while epidermal cells that con- 
tain brown contents act as shades. The special value of the paper is in its appli- 
cation for the first time of quantitative methods, instead of deductive reason- 
ing.—C. R. B. 
Turgor and curvature.—The old problem has been again attacked by KErR- 
STAN,*? namely the question whether, under tropistic stimulation, there first 
occurs a variation in turgor that causes the curvature, both in growing parts 
and in motor organs. The evidence accumulating has been all against the idea, 
stood almost alone. Kerrstan adds his testimony that in most cases there is no 
acceleration of geotropic and heliotropic growth movements by a heightened 
turgor, and often the cells of the convex side become less turgid. When such 
ric, a very slightly heightened turgor was found in curved petioles, and 
he could be observed in the imperfect organs of Malvaceae.—C. R. B. 
ere eens . 
a Seager K., Ueber den Einfluss des geotropischen und heliotropischen Reizes 
Turgordruck in den Geweben. Beitr, Biol. PAl. 9:163~213- 1907- 
