interval of time, only a slight effect.  On the other hand, the leaves which had been immersed in the solutions of the chloride of rubidium and magnesium, of acetate of strontium, nitrate of barium, and citric acid, were quickly acted on by the phosphate.  Now was water absorbed from these five weak solutions, and yet, owing to the presence of the salts, did not prevent the subsequent action of the phosphate?  Or [page 216] may we not suppose* that the interstices of the walls of the glands were blocked up with the molecules of these five substances, so that they were rendered impermeable to water; for had water entered, we know from the ten trials that the phosphate would not afterwards have produced any effect?  It further appears that the molecules of the carbonate of ammonia can quickly pass into glands which, from having been immersed for 20 m. in a weak solution of sugar, either absorb the phosphate very slowly or are acted on by it very slowly.  On the other hand, glands, however they may have been treated, seem easily to permit the subsequent entrance of the molecules of carbonate of ammonia.  Thus leaves which had been immersed in a solution (of one part to 437 of water) of nitrate of potassium for 48 hrs.—­of sulphate of potassium for 24 hrs.—­and of the chloride of potassium for 25 hrs.—­on being placed in a solution of one part of carbonate of ammonia to 218 of water, had their glands immediately blackened, and after 1 hr. their tentacles somewhat inflected, and the protoplasm aggregated.  But it would be an endless task to endeavour to ascertain the wonderfully diversified effects of various solutions on Drosera.

Alcohol (one part to seven of water).—­It has already been shown that half-minims of this strength placed on the discs of leaves do not cause any inflection; and that when two days afterwards the leaves were given bits of meat, they became strongly inflected.  Four leaves were immersed in this mixture, and two of them after 30 m. were brushed with a camel-hair brush, like the leaves in the solution of camphor, but this produced no effect.

* See Dr. M. Traube’s curious experiments on the production of artificial cells, and on their permeability to various salts, described in his papers:  “Experimente zur Theorie der Zellenbildung und Endosmose,” Breslau, 1866; and “Experimente zur physicalischen Erklrung der Bildung der Zellhaut, ihres Wachsthums durch Intussusception,” Breslau, 1874.  These researches perhaps explain my results.  Dr. Traube commonly employed as a membrane the precipitate formed when tannic acid comes into contact with a solution of gelatine.  By allowing a precipitation of sulphate of barium to take place at the same time, the membrane becomes “infiltrated” with this salt; and in consequence of the intercalation of molecules of sulphate of barium among those of the gelatine precipitate, the molecular interstices in the membrane are made smaller.  In this altered condition, the membrane no longer allows the passage through it of either sulphate of ammonia or nitrate of barium, though it retains its permeability for water and chloride of ammonia. [page 217]