THE OEDOGONIACEAE 15 
this is found in varying amounts another compound, resembling 
chitin. In Bulbochaete and Oedogonium the latter substance 
does not appear on the holdfast cell or dwarf male at the points 
of attachment. The cell may frequently be so heavily incrusted 
with lime that identification is not possible in that condition. 
The addition of warm lactic acid removes the calcium carbonate 
without undue change to the filament. Epiphytic small alge, 
including species of Oedogonium and Bulbochaete, are com- 
monly found attached to the rigid filaments. Fungal parasites, 
particularly certain Chytridiales, attack the plants both 
internally and externally. 
The vegetative cells are uninucleate with an elaborate 
parietal, reticulate chloroplast having one to many scattered 
pyrenoids. The chloroplast is quite variable in form, the 
network being considerably attenuated or hardly visible in 
the compact cylindrical mass (Carter, as reported by Fritsch 
and West, 1927). 
A rather peculiar characteristic of the family is the method 
of division of the vegetative cell which results in the so-called 
“‘apical caps.’’ Previous to the actual division there appears 
a ring-like thickening of the inner wall of the cell near its upper 
extremity. The growth of this ring ruptures the old wall 
circularly, and the outer layer of the ring becomes the new 
piece of cell wall. In the meantime nuclear division is followed 
by the formation of a cross wall at the middle of the cell, not 
connected at first with the cylinder. Later the septum assumes 
a permanent position near the lower part of the ruptured wall. 
The upper cell thus formed has a wall made up chiefly of the 
stretched ring, while the wall of the lower cell consists almost 
wholly of the lower part of the old cell membrane. The uprer 
cell, however, has at its upper extremity a part of the old cell 
wall which projects slightly, forming the cap. This apical 
cap is an excellent diagnostic character of the genus Oedo- 
gonium, although in some of the smaller species it is difficultly 
visible; and the number of caps in each cell denotes the number 
of divisions it has undergone. (Cf. Pl. LXI, figs. 598-600). 
In Bulbochaete there is rarely more than one apical cap to 
each cell, indicating, as will be explained later, that vegetative 
division in that genus occurs usually but once in a cell. (Cf. 
Pl. X, fig. 99). 
In Oedocladium usually only the terminal cell undergoes 
division as outlined above for Oedogonium. Intercalary growth 
