Proceedings of the Ohio State Academy of Science. 297 



Class V. IsoETEAE. Quillworts. 60 species. 



Sporophyte with a short tuberous stem with a peculiar type 

 of secondary thickening and with long, erect, grass-like leaves 

 which have a ligule ; roots dichotomoits ; microsporangia and 

 megasporangia large, borne singly, sunken in the expanded bases 

 of the leaves, eusporangiate. Gametophytes very much reduced ; 

 spermatozoids spirally coiled, multiciliate. 



Order, Isoctales. 



Isoetaccae. Quillwort Family. 



24. Isoetes L. 



Aquatic or marsh plants rooting in the mud, with a short 

 2-lobed or 3-lobed stem. One species of Quillwort might pos- 

 sibly be found in Ohio. 



Class VI. Selaginelleae. Selaginellas. 500 species. 



Sporophyte dorsiventral or erect, with monopodial or ap- 

 parently dichotomous branching and dichotomous roots ; leaves 

 small, opposite or spirally arranged, ligulate ; cells often with 

 a single chloroplast ; sporophylls in bisporangiate cones, the 

 eusporangiate microscorangia and megasporangia single in the 

 axils of the sporophylls. Gametophytes small and short-lived ; 

 spermatozoids very minute, biciliate. 



Order, Selaginellales. 



Selaginelldceae. Selaginella Family 



25. Selaginella Beauv. 



Terrestrial annual or perennial plants with branching stems 

 and scale-like leaves, either 4-ranked or many-ranked. 



] . Leaves all alike and uniformly imbricated and many-ranked, the 

 stem much branched in close tufts 5. rupestns. 



1. Leaves 4-ranked, shorter above and below, stipule-like, the lateral 

 ones spreading into two planes; plants small and delicate.. .S. apus. 



