270 MR. C. DARWIN ON THE ACTION OF 
stomata include grains of chlorophyll; but these, after the leaf 
has been immersed in the carbonate, almost always beeome fused 
into a few nearly colourless spheres. 
Sections made from leaves which had been left for 22 hours in 
a solution of 4 to 1000 exhibited, in the upper and lower epi- 
dermal cells of the disk, and in the cells of the parenchyma 
near the bases of the exterior tentacles, greenish spheres; and 
in such cells there were no chlorophyll-grains, but they were 
still present in some few of the epidermal cells which did not 
contain aggregated masses, and they abounded in the parenchyma 
in the middle of the disk, where there were only a few green 
spheres. These sections were irrigated with the solution of 
iodine, and the green spheres became yellow ; and many minute 
elliptieal particles of starch, coloured blue, could now be seen. 
Such particles were not visible in the sections of fresh leaves, 
and I believe that they had been imbedded within the chloro- 
phyll-grains, from which the enveloping protoplasm had been 
withdrawn to form the green spheres. 
One of the above leaves was left in the ammonia solution for 
three days, by which time it had become flaccid, being evidently 
killed. The numerous green spheres were blackened, but per- 
fectly retained their outlines. No chlorophyll-grains could be 
seen, but many particles of starch. When leaves were left for 
some time in a solution of 7 to 1000, much pulpy green matter 
and innumerable spheres were sometimes formed, but no large 
aggregated masses; so that in these cases the solution appeared 
to have been too strong. The degree to which the grains of 
chlorophyll are acted on varies much from unknown causes; 
for in some tentacles, which exhibited strongly-marked aggrega- 
tion after being left for 36 hours in the stronger solution, the 
grains could still be seen, but only after they had been cleared 
by immersion in acetic acid. 
A leaf was laid on a glass plate kept in a damp chamber, and 
two or three tentacles at one end were covered with thin glass, 
so as to prevent their bending, and were irrigated with the am- 
monia solution of 7 to 1000. After 24 hours and 48 hours these 
tentacles included many dark-purple aggregated masses; never- 
theless plenty of chlorophyll-grains were still visible. In the 
disk of this leaf, however, near the bases of these tentacles, there 
were some spheres of a fine green tint, and others purple in the 
centre surrounded by a distinctly defined green zone; and in 
