56 OUR NATIVE FERNS AND THEIR ALLIES. 



group; that the second like the first contains plants with a 

 highly organized structure; that the third is like the first two 

 in including plants with a distinct leafy axis, but differs in pos- 

 sessing a less complicated structure ; while the last diflfers from 

 all the others in having no distinction of stem and leaves. To 

 bring out these and other characters more fully, and at the 

 same time to indicate some hints of the leading subdivisions of 

 these great groups of plants, will necessitate a more technical 

 and tabular arrangement. 



1 26. The Thallophytes include the lower forms of vege- 

 tation whose plant-body varies from a unicellular condition, 

 through filamentous forms to a more or less highly differ- 

 entiated thallus. While some forms, especially among the 

 higher algae, assume the habit of a leafy-stemmed plant, none 

 attain to a true differentiation into stem and leaves. The 

 thallophytes, excludmg some anomalous groups, may be arranged 

 in three series : 



1. SCHIZOPHYTES, or fission plants, reproducing by simple 

 division and either unicellular or made up of thread-like fila- 

 ments. Two groups are included here : 



(a) Cyanophycea (blue-green algae, nostocs, etc.). 

 (F) Schizomycetes (bacteria). 



2. Alg^, or seaweeds, with mostly sexual methods of repro- 

 duction and with the plant body varying in structure from a 

 simple cell to a highly differentiated thallus or thalloid shoot.* 

 Three classes are distinguished which may usually be recognized 

 by their color. 



(a) Chlorophycea (green algae). 

 ip) Phceophycea (brown algae). 

 {f) RhodophycecB (red algae). 



3. Fungi, including moulds, mildews, and mushrooms, dif- 

 " — — - ^ 



* The American student is very poorly provided with elementary systematic 

 literature relating^ to the algae. 



Farlow : Marine Algas of New England (Report U. S. Fish Comm. 

 1879), partially covers a limited area of marine forms. For the fresh-water 

 forms Wolle: Fresh-water Algse of the United States, is the only work that 

 has attempted to cover this ground. 



