404 
the other, and is apparently continuous with the external edge of 
the dark space which defines and separates the optical sections of 
the projecting ridges. 
Mesembryanthemum crystallinum. (Cultivated.) The chroma- 
tophores here seem to have a spongy structure similar to that of 
the chlorophyll-grains of the two plants previously mentioned, but 
they are so sensitive to adverse influences that, although the tra- 
becular appearance is conspicuous and distinct, it may possibly be 
produced by another cause. The 4 per cent. solution of sugar 
sometimes distorts the chloroplasts, and disintegrates them speed- 
ily; water often acts even more quickly, and when they are forced 
out of the cell and examined in the cell-sap, the changes are 
almost as rapid and disastrous to their integrity of form and of 
structure. Yet,although necessarily examined insuch unpropitious 
surroundings, they seem to possess the pitted surface and the deli- 
cate enveloping membrane. 
Heliotropium Peruvianum . (Cultivated.) The chromato- 
phores are here prominently trabecular, or spongy in structure. 
An enveloping membrane can be demonstrated at the periphery 
of an optical section. : 
Begonia sempervirens. (Cultivated.) Here the chlorophyll- 
grains are large and the reticulated structure is prominently de- 
veloped. At this writing I have not seen the chloroplasts of eed 
plant so conspicuously pitted, and, as I am convinced, so plainly 
cancellated in structure throughout the entire chromatophore- It 
is not a difficult task practically to cut successive optical sections 
from the upper surface of the chloropast to the lower, and in these 
circumstances, with these special objects, the cancellous seul 
extends through the whole body and is not mere surface pitting: 
These chlorophyll-grains offer one of the most convincing demon 
strations of this interesting point that I have thus far observed. 
Here, as elsewhere, the green coloring-matter is not contain ie 
in the meshes of the structure, the meshes being the spaces formed 
and bounded by the threads or bands which. together form us 
chromatophore, but is within those filaments themselves. a 
meshes, by the correct focus of the objective, are jet black. ee 
A membrane also seems to surround the chlorophyll-grains © 
this variety of Begonia, but is not commonly visible, being dene™ 
_ strable only with certain of the larger chromatophores. 
