446 
The Ohio Naturalist. 
[Vol. IX, No. 4, 
THE CLASSIFICATION OF PLANTS, IV. 
John H. Schaffner. 
The class concept is becoming fairly 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. 
Proto phyceae. 
1. Cyanophyceae. Blue-green Algae. 1000 species. 
Nonsexual algae with phycocvanin, 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. 
