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 sporangium developed 

 from hypodermal cells while in the leptosporangiate forms the 

 sporangia arise from epidermal cells. The other Homosporous 

 Pteridophytes are eusporangiate. The leptosporangiate ferns 

 appear 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 



Fig;. 1. Dia2;ram of Life Cvcle of Ordinary Fern. 



compact group consisting of but one order, the Filicales. The 

 ferns usually bear large, much compounded leaves but occa- 

 sionally the leaves are sim])le and entire. 



The horsetails are rush-like geophilous perennials with 

 jointed, mostly, hollow, simple or branched, aerial stems and 

 leaves reduced to toothed sheaths at the nodes. Soine are 

 highlv impregnated 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 ])lants 

 with numerous small scale-like, lanceolate or subulate, simple 

 leaves. There is but one order, the Lycopodiales, consisting of 

 two families. 



