CYANOPHYCE 255 
the characteristic form of the filaments of the 
parent plant. 
Spores are known in certain genera, and probably 
occur in all. They differ from the ordinary cells in 
their rounded form, greater size, and more granular 
contents, and their thick, coloured membrane. On 
germination the contents shrink from the wall and 
divide by parallel walls into a number of cells, and 
this short filament escapes by a perforation or cir- 
cumscission from the parent membrane. It then 
becomes practically a hormogonium, and thus repro- 
duces the plant. In a fresh-water form, Sacconema, 
the spore divides by perpendicular walls and gives 
rise toa globular colony like Glawocapsa, but Borzi, who 
records the observation, did not observe the develop- 
ment of this body into the normal form. 
Homocystew or Oscillarvec. 
General Characters—The characters which dis- 
tinguish the Homocystee from the Heterocystew are 
mainly negative; they have no heterocysts and no 
spores. Their reproduction is solely by hormogonia. 
The Thallus——True branching, as in the Strosi- 
phonew, does not occur ainong the Homocystew, and 
since there are no heterocysts, there is no false 
branching of the type produced in the Heterocystew 
by the adhesion of the heterocyst to the sheath. 
Accordingly, in some of the genera the filaments 
remain simple, but false branching occurs frequently in 
the tribe Vaginariee and in Plectonema (Lyngbyce). 
The false branching in the former case arises when 
