IOWA ACADEMY OF SCIENCE 
51 
Of the above classes of Algae the Phaeophyceae and the Rho- 
dophyceae have no recorded representative in our flora and are not 
included in a discussion of the various classes. 
Class I. 
MYXOPHYCEAE (CYANOPHYCEAE) . BLUE GREEN ALGAE. 
The members of this class, usually easily distinguished by their 
characteristic blue green color, are almost ubiquitous in distribu- 
tion in our flora. Wherever there is moisture, on the trunks of 
trees, on rocks, on damp soil, either alone or as one of the sym- 
bionts of the lichen body, as well as in water both in stagnant and 
running. Even in the soil they are present, at least in the form 
of spores or resistant cells of some character. 
KEY TO THE SUBCLASSES OF MYXOPHYCEAE. 
I. Cells with a low type of chromatophore, often scarcely differentiated and 
with a primitive type of nucleus Archiplastideae 
II. Cells with a distinct and highly differentiated type of chromatophore and 
with true cell nucleus Glaucocystideae 
Subclass I. 
Archiplastideae. 
This subgroup includes all the blue green algae that have been reported 
from the state. 
KEY TO THE ORDERS OF THE ARCHIPLASTIDEAE. 
I. Plants unicellular or colonial, commonly imbedded in gelatinous matrix, 
more rarely free floating Coccogoneae 
II. Plants filamentous, filaments simple or branched, generally consisting of 
one or more rows of cells within a sheath attached to a substratum or 
free floating Hormogoneae 
Order I. 
Coccogoneae. 
KEY TO THE FAMILIES OF COCCOGONEAE. 
I. Cells epiphytic, with a distinct base and apex; reproduction by the forma- 
tion of gonidia only Chamaesiphonaceae 
II. Cells or colonies free floating or forming a gelatinous stratum very rarely 
epiphytic, not differentiated into base and apex, multiplication by simple 
cell division, very rarely by means of gonidia Chroococcaceae 
