Proceedings of the Ohio State Academy of Science. 275' 



12. Vascular bundles 2, often uniting, not incurved; sori on specialized 



leaves; pinnules pinnately veined, barely dicliotomous 



Mattcitccia (18) . 



12. Vascular bundles strongly incurved, venation distinctly dichotomous. 



13. 



13. Sporangiophore distinct, usually on a stalk beside tbe leafblade; 



sporangia large, globular Botrychimn (2). 



13. Sporangia on specialized leaflets at the end or sides of the foliage 



leaves; or on specialized leaves; vascular bundle in base of 

 petiole 1; leaves 2 or more feet long, bipinnatifid or bi- 

 pinnate Osmunda (3) . 



14. Sori with marginal indusia formed by the more or less altered and 



reflexed edge of the leaflet or its lobes. 15. 



14. Sori with special indusia or naked, not covered by the margin of the 



leaflet. 16. 



15. Only the tips of the lobes of the leaflets reflexed as indusia. 



Adiantum (5). 



15. Entire margin of the leaflets reflexed to form the indusium, rarely 



interrupted Pellaea (7). 



16. Sori linear or oblong, indusia more than twice as long as broad. 17. 



16. Sori round or roundish, indusia less than twice as long as broad. 18 



17. Sori elongated, on the upper sides of the veins Asplenium (9). 



17. Sori and indusia somewhat curved, sometimes horseshoe-shaped 



man}' of them crossing the veinlet, sometimes with 2 sori placed 

 back to back ; leaves bipinnatifid or bipinnate in our species, usu- 

 ally 2-3 feet long Athyritim (10). 



18. Sori naked, circular; petiole with 2 united vascular bundles; leaf 



blades triangular or ternate Phegoptcris (14) . 



18. Sori with indusia, sometimes inferior and obscure; leafblade not 



triangular nor ternate. 19. 



19. Indusium superior, cordate or reniform, attached by the sinus. 



Dryoptcris (13). 



19. Indusium convex, delicate and partly inferior, attached by a broad' 

 base at the side and enclosing the sorus like a hood ; leaves 

 sometimes with brood-buds Filix (15). 



19. Indusium wholly inferior. 20. 



20. Indusium roundish or stellate, delicate, cleft into narrow segments; 



leaves in our species usually net over 16 inches long. Woodsia (16)., 



20. Indusium cup-shaped, somewhat 2-valved ; leaves in ours usually 



over 2 feet long Dennstaedtia (17). 



