to MORPHOLOGY 
Stigonema. In some Cyanophyceae, however, true branching occurs, and 
this is illustrated by such forms as Stigonema, in which branches are started by 
lateral outgrowths from individual cells of the 
filament rather than by mechanically freeing 
some of the cells (fig. 12). 
Conclusions. A brief summary of the 
important features cf the Cyanophyceae 
may be stated as follows: 
(i) The plant body is a single cell, 
and the general tendency is to organize 
a colony of cells into the form of a simple 
filament. 
FIG. 12. Stigonema: showing ( 2 ) There is a characteristic mucilagi- 
true branching. After BORZI. ... - ,, ,. , f 
nous swelling of the walls, which favors 
colony formation by imbedding the individual cells. 
(3) The protoplast is apparently simple in organization, giving no 
evidence of distinct chloroplasts, and with a nucleus ordinarily not 
sharply limited by a membrane, both of which features are in contrast 
with the protoplasts of true algae. 
(4) There is some differentiation of cells, notably in the formation 
of heterocysts; and differentiation reaches its extreme expression in 
such forms as Rivularia, with base and apex. 
(5) The power of locomotion is evident in the group, notably in 
Oscillatoria, and also in connection with colonization by means of hor- 
mogonia. 
(6) The only method of reproduction known is vegetative multipli- 
cation, and the cell divides by an ingrowing wall plate. 
(7) Protection against unfavorable conditions is provided for by 
the transformation of ordinary vegetative cells into resting cells, the 
chief changes being enlargement, accumulation of reserve food, and a 
heavy wall. 
(2) SCHIZOMYCETES 
General description. The name means fission fungi, and corresponds 
in form to Schizophyceae (fission algae), a name often applied to the 
blue-green algae. However, they are best known as bacteria. The 
group has many characters in common with the Cyanophyceae, such as 
the one-celled body which often forms filaments (colonies), a protoplast 
of simple structure, the tendency in certain conditions to produce a 
mucilaginous matrix that embeds the cells, the power of locomotion, and 
