446 The Ohio Naturalist. [Vol. IX, No. 4, 



THE CLASSIFICATION OF PLANTS, IV. 



John H. Schaffxer. 



The class concept is becoming fairlv well established in botany 

 even though one frequently finds groups of very unequal rank 

 designated as classes in recent works. In the last article of the 

 present series of papers, the writer defined a class as "A group of 

 plants in a subkingdom. the members of which show an evident 

 relationship to one another because of similarity of morphologi- 

 cal and physiological characters." A diagram was also given 

 showing the approximate relationships of the classes. 



There are between forty and fifty plant classes. Of course, 

 it will be recognized that the groups we call classes are of the 

 same rank only in a general sense. In the following scheme forty- 

 six classes, four of them fossil, have been established and are 

 characterized by brief descriptions together with the approxi- 

 mate number of species. The endings of the fungus names 

 have been changed to correspond to Saccardo's views. There 

 should be a uniform system of class endings, but this will come 

 probably only when the class becomes more definitely recognized 

 as a plant group. It might be well in the future to revise some 

 of the class names now in use. It is manifestly absurd to 

 attempt to apply the law of priority in establishing class names. 

 Until very recently the very idea of the class as a definite group 

 from the modern point of view was lacking and our .system of 

 the larger groupings is still in its evolution. The arguments 

 adduced for priority in establishing generic and specific names 

 have no weight when applied to the higher groups. From time 

 to time some botanist proposes an improvement and it is thus 

 that a reasonable system will be developed. 



In a future paper an attempt will be made to group the classes 

 into proper phyla in harmony with the diagram already published. 



I. PROTOPHYTA. 3000 species. 



Protophyccae. 



1. Cyanophyceae. Blue-green Algae. 1000 species. 

 Nonsexual algae with ph3'coc3^anin, blue-green or brownish 



in color; unicellular, in plates or masses, or in simple or branched 

 filaments; reproduction by simple fission or hormogones, some- 

 times with specialized resting cells ; cell walls usually gelatinous. 

 Typically freshwater plants, frequently occurring in hot springs, 

 some growing in aerial conditions on moist soil, rocks and trees. 



2. Pleurococceae. 200 species. 



Simple nonsexual green algae, unicellular, filamentous, or in 

 colonies; reproduction by fission, by internal division, or by 

 zoospores. Typically freshwater or aerial plants. 



