328 THE PLANT PHYLA 
KEY TO THE PHYLA OF PLANTS 
In this key only the general or typical characters are indi- 
cated, and it must be remembered that many variations 
(‘‘exceptions’’) occur in every phylum. 
A. Cells typically with poorly developed nuclei and chromato- 
phores; reproducing by fission and spores; 
mostly blue-green, brown-green or fuliginous 
(or colorless), never chlorophyll green. 
I. Unicellular to filamentous plants. 
Phylum 1. Myxopuycrag. 
B. Cells typically with well-developed nuclei and chromato- 
phores (chloroplasts); reproducing by fission 
and spores, and mostly by gametes also; 
chlorophyll-green, sometimes hidden by other 
coloring matter (or colorless). 
I. Plants usually of but one obvious generation, typi- 
cally aquatic. 
a. The fertilized egg developing into a zygote only. 
1. Unicellular, to filamentous, many-celled plants 
(rarely a plate of cells); isogamic to hetero- 
gamic, one or both gametes ciliated. 
Phylum 2. CHLOROPHYCEAE. 
2. Filamentous many-celled plants, mostly break- 
ing up early into single cells; isogamic, gam- 
etes not ciliated. Phylum 3. Zy@orHycEAk. 
3. Tubular filamentous (or saccate) coenocytic 
plants, usually attached basally by rhizoids; 
isogamic to heterogamic. 
Phylum 4. SrpHONOPHYCEAE. 
4. Cellular filamentous (rarely unicellular) to 
massive plants, attached basally by rhizoids 
(or roots); isogamic to heterogamic; the 
green color hidden by a brownish pigment. 
Phylum 5. PHAEOPHYCEAE. 
b. The fertilized egg developing into a spore-fruit. 
1. Cellular filamentous to massive holophytic 
plants, attached basally by rhizoids (or 
roots); heterogamic; the green color mostly 
hidden by a red or purple pigment. 
Phylum 6. RHODOPHYCEAE. 
