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1913] Blanchard, — Two new Species of Stigonema 193 
The plant in the vegetative condition consists of blue-green fila- 
ments, 20-36 microns wide, that are repeatedly branched in every 
direction. Occasionally three or four branches may arise from adja- 
cent cells, but the branches are usually more scattered. Although it 
is usually true that a branch is narrower than the filament it comes 
from, it may be equal to it in width, but never greater. In all the 
material collected the majority of branches appeared to be developed 
for the sole purpose of forming hormogones. No free vegetative ends 
of filaments, that were not forming or that had not already formed 
hormogones, were observed in all the material examined. The fila- 
ments are usually composed of a single row of cells, but two cells very 
frequently occur side by side. The colorless connections between 
the cells are plainly shown in formalin preserved material (fig. 8). 
Lateral heterocysts are common (fig. 3). Intercalary heterocysts 
often occur just below a hormogone, and sometimes in other places, 
but they are less common than the lateral heterocysts. They contain 
no granules and vary in color from a light brown to a very dark blue. 
The sheath is usually colorless, but many times is tinged at the ends 
of branches with a light, golden brown. The sheath varies from four 
to eight microns in thickness. 
Filaments grow in length and develop branches by simple division 
of cells. Early stages in formation of a branch are shown in figures 1, 
2, and3. Hormogones are found of all lengths up to 196 microns, and 
their width is the same as that of the vegetative cells. They are 
developed in special branches and at the ends of main branches; they 
may occupy the whole of a branch and project down into the main 
filament, or may occupy only a part of the branch (figs. 3 and 6). 
When the plant is most actively forming hormogones, the vegetative 
cells become more and more vacuolated (figs. 1, 2, 3, and 6), and after 
the hormogones have escaped, the vegetative cells, sometimes if not 
always, degenerate. In one plant observed, every hormogone had 
escaped, and the sheath and cells had become a uniform brown, show- 
ing evident degeneration after escape of hormogones. Intermediate 
stages in this degeneration are easy to find. 
The hormogones escape by a breaking off of the end of the sheath 
as in figure 6, or by apparent disorganization of the end of the sheath. 
The actual discharge of the hormogone is a slow process and appears 
to be accompanied by the discharge of a mucilaginous mass (figs. 
4 and 5). The hormogone may escape from the sheath as a whole or 
