. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. EXPERIMENTS OF PPEFJTBR. 227 or clay cell, like those which are used in tlie Buusen battery, connected bj' means of a glass collar with a suitable manometer. Within the cla^- cell a precipitation film is formed; 'â the cell is ' The following account of details essential to success in these experiments of Prof. Pfeffer has been prepared by one of his students, Dr. W. P. Wilson. The principal portion of the apparatus is a porous porcelain cell, z, 46 mm. high a
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. EXPERIMENTS OF PPEFJTBR. 227 or clay cell, like those which are used in tlie Buusen battery, connected bj' means of a glass collar with a suitable manometer. Within the cla^- cell a precipitation film is formed; 'â the cell is ' The following account of details essential to success in these experiments of Prof. Pfeffer has been prepared by one of his students, Dr. W. P. Wilson. The principal portion of the apparatus is a porous porcelain cell, z, 46 mm. high and 16 mm. in diameter, with walls 1^ mm. in thickness. This cell is cemented on to a piece of glass tubing, v. A second piece of tubing, t, with lateral tube, is cemented into the tirst piece. The lateral opening is for the manometer m, the one at g is for the convenience of tilling and sealing the cell. One of the two fluids used in forming the membrane for experimentation is allowed to penetrate the porous cell from without. When this has thoroughly taken place, the second fluid is poured into the interior. The contact of the two fluids takes place, there- fore, on the inner surface of the porous cell, and here the precipitate is formed which is termed the pellicle-vutnbrane or precipita- tion-membrane. Substances which by their mutual contact give rise to such precipitation- membranes are termed membranogenic. It will readily be seen that during any internal pressure the porous porcelain cell acts as a support for the membrane. If the exterior solution is copper-sulphate, the interior solu- tion potassic ferrocyanide, then the precipi- tated membrane will be cuprio ferrocyanide. After the membrane has been fonned, then any solution not chemically incompatible with it may be employed in the cell; namely, syrup from cane-sugar, a solution of saltpetre, or a still stronger solution of potassic ferro- cyanide than was used in the preparation of the cell. 143 As the successful
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