400 
tain diatoms are familiar with the fact that when the whitish pearls 
have become black dots by the proper focussing, the edges of the 
black apertures are not always sharply cut; in fact there is no actual, 
well-defined edge to the opening, but it is approached by a concave 
slope, a smooth depression which surrounds the black aperture 
and leads to it. A homely comparison may be made by thrusting 
the finger-end into stiff dough, when the resulting depression will 
show an evenly rounded approach similar to that so readily obser- 
vable in certain diatoms. A similar condition exists with the de- 
pressions on the chromatophores of this moss. 
This spongy aspect is not an optical illusion produced by 
minute granules or other objects within the protoplasm of the cell. ie 
The pits and the laterally projecting bars are as conspicuous 
when the chromatophore has been forcibly extruded and is float- 
ing freely in the mounting medium as they are while within the 
living cell. But the pits are exceedingly shallow ; and the narrow 
ridges are correspondingly low, for I have not been able to measure 
them with the ordinary micrometer, as the lines made by the 
diamond are so broad in comparison that they obliterate the bar- 
like points of the optical section. . 
That the chromatophores of all plants are trabecular in struc 
ture is not yet to be written. In many of our common plants 8 
cannot be demonstrated. In those of Astrophyllum sylvaticum 
there can be no doubt of the trabecule. : 
There has also been some discussion and some disparity 
of opinion as to the existence of a membrane surrounding the 
chlorophyll-grain. That all chromatophores are surrounded by 4 
membrane is another assertion which must be put to the test by . 
examining the chlorophyll-grains of all species of plants. Yet - 
Tschirch says* that after experiments on the living cells of ee 
(Anacharis) and of Nitella he is convinced that all chlorophylr 
bodies and aleurone-grains are ‘surrounded by an envelope: pres 
peating this statement in another placet he adds that the inte 
matter of two different grains never comes into contact. a 
a part of the morphology of the chlorophyll-grains of Astrophylium 
sylvaticum, and of those in some other plants. Yet in the mo : 
* Ber. Deutsch. Bot. Gesell. x : (1883). 
{ Ib. 2: 26s. 
