484 
The Ohio Naturalist. 
[Vol. VI, No. 5, 
The ferns are divided into two distinct subclasses called the 
Eusporangiatae and Leptosporangiatae. The eusporangiate 
ferns have the spore bearing tissue of the s])orangiuni developed 
from hypodermal cells while in the leptosporangiate forms the 
sporangia arise from epidermal cells. The other Homosporous 
Pteridophytes are eusporangiate. The le])tosporangiate ferns 
a])pear after the Paleozoic Era and are at present by far the 
most abundant. There are two orders of Eusporangiatae, the 
Ophioglossales and Marattiales. Some authors have attempted 
to associate the Ophioglossales with the Lycopods, but from a 
consideration of all their characteristics it does not appear that 
there is any evident relationship. The Leptosporangiatae are a 
compact group consisting of but one order, the Filicales. The 
ferns usually bear large, much compounded leaves but occa- 
sionally the leaves are simple and entire. 
The horsetails are rush-like geoidiilous i)erennials with 
iointed, mostly, hollow, sim]de or branched, aerial stems and 
leaves reduced to toothed sheaths at the nodes. Some are 
highly im])regnated with silica and are hence called scouring 
rushes. They are closely related and constitute but a single 
order, the Equisetales, with a single family and genus. 
The lycopods are small herbaceous often geophilous jdants 
with nunaerous small scale-like, lanceolate or subulate, simple 
leaves. There is but one order, the Lycopodiales, consisting of 
two families. 
Fig. 1. Diagram of Life Cycle of Ordinary Fern. 
