Proceedings of the Ohio State Academy of Science. 271 



Classes, Filices, 



Hydropterides, 

 Isoeteae. 



2. Caloniophyta. 25 known living species. Vascular seed- 

 less plants with jointed stems and small whorled leaves with 

 comparatively large multiciliate sperms, ai:d with the sporophylls 

 in cones. 



Classes,' Ecjniseteae, 



Sphenophylleae (Fossil), 

 Calamarieae ( Fossil ) . 



3. Lepidophvta. 660 known living species. Vascular seed- 

 less plants W'ith simple, usually small leaves covering the stem, 

 with small biciliate sperms, and with the sporophylls in cones 

 or sometimes forming zones alternating with the sterile leaves. 



Classes, Lycopodieae. 

 Selaginelleae. 



KEY TO THE CLASSES OF HOMOSPOROUS AND 

 HETEROSPOROUS PTERIDOPHYTES OF OHIO. 



1. With comparatively large, broad, compound or rarelj^ simple, abun- 

 dantly veined leaves; homosporous, the spores all of one kind; 

 sporangia borne on the foliage leaves or on special sporangio- 

 phores I. Filices. Ferns. 



1. With 4-foliate, slender-petioled leaves from a horizontal rhizome; 

 or small, free-floating plants with small 2-ranked foliage leaves ; 

 heterosporous, the spores of two sizes, microspores and megaspores ; 

 sporangia in sporocarps IV. Hydropterides. Water-ferns. 



1 . Leaves small, short, and scale-like, scattered or in whorls ; or long, 

 grass-like, and in a rosette; plants not floating; homosporous or 

 heterosporous. 2. 



.2. With minute scale-like leaves in a whorl, forming sheaths at the 

 nodes of the jointed stem; homosporous, the spores with append- 

 ages, the peltate sporophylls in cones 



II. EouiSETEAE. Horsetails and Scouring Rushes. 



