THE PYRENOID OF ANTHOCEROS 
83 
Description of Observations 
The material for this study was collected in the vicinity of Ithaca, 
N. Y., in August, 1912. The fixation was carried on with the aid of 
an air pump, thus insuring quick penetration of the fixative into the 
intercellular cavities of the thallus. The killing agents used were 
Flemming's strong osmic acid mixture, medium strength osmic acid 
mixture as used by Strasburger, and Merkel's killing solution. 
For the study of starch formation Merkel's solution gave rather the 
best results. The hydrogen peroxide bleaching mixture apparently 
exerts a weak hydrolytic action for a few days' exposure of preparations 
of Anthoceros, Conocephalum, Reboulia, and other liverworts contain- 
ing starch to the ordinary bleaching solution (hydrogen peroxide one 
part and 50 per cent alcohol one part) is sufficient to remove all of 
the starch, or at least to render it incapable of staining either with 
iodin or with Flemming's triple stain. In order therefore to keep the 
starch as nearly as possible as it is in the living cell it is desirable to 
avoid the use of killing solutions which necessitate a bleaching of the 
fixed material. Merkel's solution answers this requirement, and other 
than a slight difficulty in staining achromatic figures following its use, 
this killing agent compares very well indeed with the osmic acid 
mixtures. 
The chloroplast of the gametophyte of Anthoceros laevis is, in gen- 
eral, lens- or disc-shaped (figures i and 4). The thickness of the disc 
varies greatly, ranging from more than half its diameter to less than 
one eighth (figures 2 and 3). As will be suspected, the thicker chloro- 
plasts are associated with abundant starch formation and are to be 
found in the mature areas of the thallus and close to the surface, while 
the flatter plastids seem to be located in cells which are more or less 
dormant and in the interior cells of the thick, mature thallus. Usually 
the surface of the disc next to the cell wall is convex while there is a 
tendency toward concavity on the side facing the vacuole, though a 
noticeable bulge is nearly always present opposite the pyrenoid. 
The chloroplast varies in size according to the size of the cell 
in which it is situated. In the region of the growing point where the 
cells are small, the plastids measure about 10 microns in diameter by 
4 in thickness (figure 6). In the large cells of the fully grown areas 
of the thallus they may be as large as 40 by 15 microns (figure 8). 
Near the central part of the chloroplast, though somewhat nearer 
the vacuole than the cell wall, is located a more or less compact group 
