THE PYRENOID OF ANTHOCEROS 
89 
The starch is formed with no apparent increase in the size of the 
chloroplast. It is formed in disc-shaped masses which may He in any 
part of the plastid and in any position. More commonly they Ue 
near the periphery of the plastid or they may extend across the central 
region as flattened bi-convex discs (figures 21 and 22). Usually from 
three to ten of these disc-shaped starch grains are present. Plastids 
filled with starch have much the same general appearance as plastids 
to be found in the region of the foot in the sporophyte of Anthoceros 
(figure 12). Those of Reboulia are however smaller and have fewer 
starch grains. These figures of the plastids of Reboulia are very 
similar to the well known figures of Sachs for Funaria, both as to the 
shape of the starch grains and as to their distribution. 
Discussion 
As has been shown, the so-called pyrenoid of Anthoceros is in no 
case homogeneous as in the green algae but is at all times a more 
or less crowded mass of disc or spindle-like bodies. Lutman (11) has 
found that in Closterium the entire pyrenoid occasionally breaks up 
''into lens-shaped segments." In this segmented condition these 
pyrenoids may remotely resemble the multiple pyrenoids of Antho- 
ceros. It seems quite possible however that these lens-shaped seg- 
ments are indicative of the conversion of the entire pyrenoid into a 
number of starch grains as has been described for Oedogonium and 
Rhizoclonium (21) and for Tetraspora (12). In any case they are not 
persisting structures of the plastid as is the case with the pyrenoid 
bodies of the pyrenoid of Anthoceros. 
On the other hand the chemical nature of the bodies making up 
the Anthoceros pyrenoid seems to be the same as that of the pyrenoids 
found in the algae. Both give positive results with microchemical 
tests for protein. These protein bodies serve as the foundations or the 
groundwork of the starch grains and are converted into starch with 
no change in form, and, at first, no change in size. According to 
Timberlake (21) the pyrenoids of Rhizoclonium, Oedogonium, and 
Cladophora become at times entirely transformed into a single large 
mass of starch. This is also frequently the case in Tetraspora (12). 
The mode of starch formation from these pyrenoids is then at times 
the same as it is in Anthoceros from the single pyrenoid bodies. It 
must not be lost sight of however that here the comparison is between 
the entire pyrenoid of the above mentioned algae and a single pyrenoid 
