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. MYXOPHYCEAE. 



B. Cells typically with welt-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. ZYGOPHYCEAE. 



3. Tubular filamentous (or saccate) coenocytic 



plants, usually attached basally by rhizoids; 

 isogamic to heterogamic. 



Phylum 4. SIPHONOPHYCEAE. 



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. 



