CURRENT LITERATURE. l43
solution of some hard varnish and drawing on the varnish surface with a clean pen and India ink. The slides may be used unbound, or they may be bound in the usual manner for permanence.
Osterhout, W. J. V. and A. R. C. Haas. A simple method of measuring photosynthesis. Preliminary note. Science N. S. 47 1918 pp. 420-422.
To a large amount of water add a little phenolthalein and sodium bicarbonate till a barely perceptible pink color is developed. Some of the solu- tion freshly made is put into a small tube with a branch of an aquatic plant. When the tube is placed in sunlight the color of the solution soon becomes bright pink, as the result of removal of C0 2 from the water during photosyn- thesis. Under proper conditions the intensity of the colour may be used to estimate the amount of photosynthesis. If after the color is develop- ed, the tube is kept in darkness for some time, the solution becomes colorless again, due to the liberation of C0. 2 by respiration acting alone.
Osterhout, W. J. V. A simple method of demonstrating the pro- duction of aldehyde by chlorophyll and by aniline dyes in the presence of sunlight, dm. Jour. Bot. 5; {1918) pp. 511-513.
An alcoholic extract of chlorophyll is shaken up with carbon tetra- chloride. The carbon tetrachloride solution is then drawn oft and sprayed on filter paper. After the paper has become dry it is sprayed again, and the process is repeated till the paper becomes dark green like a leaf. The filter paper is then fitted over the entire inner surface of a large bell jar and wet with water to make it fit and adhere to the glass. The bell jar is put on a glass plate over a large petri dish containing about 5 cc. of water, and the edges are sealed vaseline. The apparatus is placed in full sunlight and left till the chlorophyll has been bleached to a pale green or pale yellow. Then the water is tested by means of Schryver's text for aldehyde, and a positive result usually is obtained.
It is of great interest that certain aniline dyes, as methly-green and iodine- green, in water solution, may be substituted for chlorophyll. It makes little difference whether CO. is present or excluded, but the presence of oxygen is necessary. The author concludes " that the aldehyde is not produced by " the decomposition of C0. 2 but rather by the decomposition of chlorophyll. It may be that this method of aldehyde formation a regular step in normal photosynthesis.
Winfjeld Dudgeon.
Physiology.
Mallock, A., Growth of Trees, with a Note on Interference Bands formed by Rays at Small Angles. Proc. Boy. Soc. B 90. (1918) No. B. 627 pp. 186— -191 with 4 fig. in text.
In this paper is described a device for the measurementiof the very minute hourly increase in girth of an ordinary tree, by its effect on the interference bands produced by the incidence of mono-chromatic light on a glass plate resting by one edge on a prison and inclined at a small angle to it. A band of invar is passed round the tree, previously smoothed a little, and made to
