2 Charles E. Bessey 



These phyla may be characterized in a general way as follows 

 by rneans of an analytical key, in which only the general or typ- 

 ical characters are indicated. In making use of it, it must be 

 remembered that many variations ("exceptions") occur in 

 every phylum. 



KEY TO THE PHYLA OF PLANTS 



A. Cells typically with poorly developed nuclei and chromatophores ; re- 



producing by fission and spores ; mostly blue-green, brown-green 

 or fuliginous (or colorless), never chlorophyll-green. 

 I. Unicellular to filamentous plants Phylum i. Myxophyceae. 



B. Cells typically with well-developed nuclei and chromatophores (chloro- 



plasts) ; reproducing by fission and spores, and mostly by gametes 

 also ; chlorophyll-green, sometimes hidden by other coloring mat- 

 ter (or colorless). 



I. Plants usually of but one obvious generation, typically aquatic. 



a. The fertilized egg developing into a zygote only. 



1. Unicellular, to filamentous, many-celled plants (rarely a plate 



of cells) ; isogamic to heterogamic, one or both gametes 

 ciliated. Phylum 2. Protophyceae. 



2. Filamentous many-celled plants, mostly breaking up early into 



single cells; isogamic, gametes not ciliated. 



Phylum 3. Zygophyceae. 



3. Tubular filamentous (or saccate) coenocytic plants, usually 



attached basally bj' rhizoids ; isogamic to heterogamic. 



Phylum 4. Siphonophyceae. 



4. Cellular filamentous (rarely unicellular) to massive plants, 



attached basally by rhizoids (or roots) ; isogamic to hetero- 

 gamic; 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. 



2. Cellular filamentous hysterophytic plants, often much degen- 



erated, without chlorophyll; heterogamic. 



Phylum 7. Carpomyceteae. 



II. Plants of two obvious, alternating generations, typically terrestrial, 

 a. Gametophyte generation larger, and longer-lived than the de- 

 pendent sporophyte generation. 



I. Gametophytes from prostrate and thalloid to erect leafy shoots; 

 sporophytes globose to cylindrical or stalked, neither ex- 

 panded nor rooted. Phylum 8. Bryophyta. 



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