176 DROSERA ROTUNDIFOLIA. [Cuar. IX, 
Tn a large majority of these twenty cases, a varying degree of 
inflection was slowly caused by the phosphate. In four cases, however, 
the inflection was rapid, occurring in less than half an hour or at most 
in 50m. In three cases the phosphate did not produce the least effect. 
Now what are we to infer from these facts? We know from ten trials 
that immersion in distilled water for 24 hrs. prevents the subsequent 
action of the phosphate solution. It would therefore appear as if the 
solutions of chloride of manganese, tannic and tartaric acids, which are 
not poisonous, acted exactly like water, for the phosphate produced no 
effect on the leaves which had been previously immersed in these three 
solutions. The majority of the other solutions behaved to a certain 
extent like water, for the phosphate produced, after a considerable 
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 
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 4387 
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 
* See Dr. M. Traube’s curious ex- precipitation of sulphate of barium 
periments on the production of arti- 
ficial 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 Erklirung der 
Bildung der Zellhaut, ihres Wachs- 
thums durch Intussusception,” Bres- 
lau, 1874. These researches perhaps 
explain my results. Dr. Traube 
commonly employed as « membrane 
the precipitate formed when tannic 
acid comes into contact with a so- 
lution of gelatine. By allowing a 
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 mole 
cular 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 per- 
meability for water and chloride of 
ammonia, 
