408 BULLETIN OF THE BUREAU OF FISHERIES. 
This division, well represented in most regions, here forms a very small part of the 
marine flora, only 10 genera and 10 species having been obtained in quantities sufficient 
for determination. 
KEY TO ORDERS. 
Plants unicellular, single, or associated in families, which are usually surrounded by a gela- 
tinous integument, not filamentous... ...............0 0. 0ce cece eee eee 1. CoccoGoNE# (p. 408). 
Plants multicellular (except Spirulina), filamentous. »..................... 2. HORMOGONE& (p. 409). 
Order 1. Coccogoneze (Thuret) Kirchner. 
Plants unicellular, single, or associated in families or colonies which are usually 
surrounded by a copious gelatinous integument, rarely forming filaments; multiplica- 
tion occurs commonly by the vegetative division of cells, rarely by the formation of four 
or more nonmotile gonidia arising from the division of the contents of a cell 
(gonidangium). 
Family 1. CHROOCOCCACEZ Negeli. 
Cells solitary or associated in families, showing no difference between basal and 
apical regions; multiplication usually by simple division of the cells. 
Unicellular alge, entirely uniform, occurring singly or more often in clusters which 
are conspicuous even to the naked eye, the cells grouped without order in a common 
sheath. Cells spherical, oval or elongate, sometimes fusiform, cuneate, or squarish. 
Extremely minute bodies containing diffuse blue, eruginous, or even purple, olive, 
brown, or yellow coloring matter occur in the cells. The cell wall is sometimes 
thin and delicate, sometimes thick, often surrounded by a structureless, gelatinous 
sheath which holds the cells together for many generations and forms families variable 
in number and appearance of the cells. Divisions usually in three planes forming 
families irregularly grouped, but also in two planes forming layers of sheetlike families, 
or even in one plane, forming families at first linear, then by mechanical action irregularly 
grouped and contorted. Propagation in the Chroococcacee living singly does not occur 
except by the vegetative division of the cells, in those species living gregariously it occurs 
either by the separation of a single cell or by the splitting up of an old family into several 
families. Spores provided with a thickened resistant wall have been observed occa- 
sionally in species of Gloeocapsa; these arise from the vegetative cells and are formed 
by the repeated division of the contents or by the dissolution of the membrane. 
About 300 species, mostly in fresh water, less often in salt water or in damp places 
or aerial, throughout the world. 
Genus Chroococcus Negeli. 
Chroococcus Negeli, 1849, D. 45- 
Cells globose, or by mutual pressure more or less angular, each surrounded by a 
more or less definite sheath; solitary or associated in families composed of two or four, 
rarely more, individuals, but not held together in definite colonies by a common gelat- 
inous sheath; cell wall thin or wide, homogeneous or lamellose, colorless or colored; 
cell contents homogeneous or granular, zeruginous or blue-green, sometimes yellowish or 
orange or violet; multiplication by successive division of the cells alternately in three 
planes; free floating or forming a gelatinous or crustlike mass in damp places. 
