3 02 THE POPULAR SCIENCE MONTHLY. 



the whole inner surface of the cell ; sometimes the quantity is smaller, 

 and they are separate. Now, it has lately been discovered that in 

 the latter case, under the influence of light, the green corpuscles we 

 speak of undergo very singular changes of position. Some twelve 

 years ago, Boehm noticed for the first time that in certain unctuous 

 plants the grains of chlorophyll gather at one point of the wall of the 

 cells under the action of the sun. He remarked that the phenomenon 

 does not take place in the dark, nor in the red rays. The flat sheet 

 made up of a single layer of cells, without epidermis, which composes 

 the leaves of mosses, seemed to Famintzin the most suitable for this 

 delicate kind of observations. He followed the movements, that take 

 place in these sheets, by microscopic study. During the day the green 

 coloring-grains are scattered about the upper and lower parts of the 

 leal-cells. At night, on the contrary, they accumulate toward the 

 lateral walls. The blue rays affect them like white light; the yellow 

 and the red ones keep the chlorophyll in the position it takes at night. 

 The order of activity in the rays seems, then, to differ in this case from 

 that in the phenomena of respiration. The researches of Borodine and 

 Prillieux proved that these movements of coloring-corpuscles within 

 the cells occur in almost all cryptogamous plants, and in a certain 

 number of phanerogamous ones. The lately-published experiments of 

 Roze show that in mosses the grains of chlorophyll are connected by 

 very slender threads of plasma, and may suggest the idea that these 

 threads are the cause of the changes of position just described. Per- 

 haps there is some real relation between them; but it must not be for- 

 gotten that these movements of the plasmatic matter inside the cell 

 take place by day and night, and that light has no marked effect on 

 them. The green particles, on the contrary, creep over the walls of 

 the cell, and move toward the lightest part as zoospores and some in- 

 fusoria do. 



Biot relates that in 1807, while at Formentera, employed in the 

 work of extending the meridional arc, he devoted his leisure hours to 

 the analysis of the gas contained in the swimming-bladder of fishes 

 living at different depths in the sea. The oxygen required for these 

 analyses was furnished him by the leaves of the cactus opuntia, which 

 he exposed in water to sunlight, under hand-glasses, ingeniously apply- 

 ing the discovery of Ingenhousz and Senebier. It occurred to him one 

 day to expose these leaves, in a dark place, to the illumination thrown 

 by lamps placed in the focus of three large reflectors, used for night- 

 signals in the great triangulation. He threw the light from three of 

 these reflectors on the cactus-leaves. The eye, placed in this concen- 

 tration of light, must have been struck blind, Biot says. The experi- 

 ment, kept up for an hour, did not cause the release of a single gas- 

 bubble. The glass was then taken into the diffused light outside tho 

 hut. The sun was not shining, but the evolution of gas took place at 

 once with great rapidity. Biot is a little surprised at the result and 



