268 MR. C. DARWIN ON THE ACTION OF 
Transverse sections of other immersed leaves presented various 
appearances. In one cell a central transparent sphere was sur- 
rounded by a halo of brown granular matter, and this again by 
à zone of the transparent matter, and such matter quite filled 
some adjoining cells. In the cells of another leaf there were, 
throughout its whole thickness, yellow, greenish, orange, pale 
or very dark-brown spheres. Some of these latter spheres had 
a dark centre, which was so hard that it was cracked by pressure, 
and the line of separation from the surrounding zone of paler 
matter was distinct. Two brown spheres were in one case in- 
cluded within the same transparent sphere. Gradations seemed 
to show that the opaque granular matter ultimately passed into 
dark-coloured transparent matter. In these same sections there 
were some colourless or yellowish highly-transparent small 
spheres, which, I believe, were merely much swollen chlorophyll- 
grains. One, two, or more of such grains, while still partly 
retaining their outlines, sometimes clung to the darker granular 
spheres. When there were only one or two of them thus cling- 
ing, they assumed the shapes of half- or quarter-moons. It 
appeared as if such swollen grains when completely confluent 
had often given rise to the pale zones surrounding the granular 
spheres. The pale zones were rendered still more transparent 
by acetic acid; and on one occasion they quite disappeared, after 
being left in the acid for 24 hours; but whether the matter was 
dissolved or had merely disintegrated was not ascertained. This 
acid produces the same effect on recently aggregated pale- 
coloured or almost colourless matter in the tentacles of Drosera. 
In one leaf a good many unaltered chlorophyll-grains could 
still be distinguished in some of the cells; and this occurred 
more frequently in the thickest part of the leaf, near the midrib, 
than elsewhere. In one section the chlorophyll-grains had run 
together, and formed in some of the cells narrow green rims 
round all four walls. In many sections, more especially in those 
in which the process of aggregation had not been carried very 
far, there was much extremely fine granular matter, which did 
not resemble smashed or disintegrated chlorophyll-grains, such 
as may often be seen in sections of ordinary leaves. This gra- 
nular matter occasionally passed into excessively minute, trans- 
parent, more or less confluent globules. 
Judging from these several appearances, we may conclude that 
carbonate of ammonia first acts on the cell-sap, producing a gra- 
