322 THE KINDS OF PLANTS 



B. Sporangia large and globose, without a ring of special 



cells running around their margin 1. Osmunda 



BE. Sporangia with a ring of prominent elastic cells run- 

 ning around the margin, and which are concerned 



in the dehiscence 2. Onoclea 



AA. Fruit borne on the back of green fronds (the fruiting 

 pinnae sometimes narrowed but still leaf-like), sporan- 

 gia with a ring of elastic cells. 



B. Sori naked (no indusium) 3. Polypodium 



BB. Sori borne under the reflexed margins of the frond. 

 c. Pinnae entire on the lower edge, somewhat trian- 

 gular in outline 4. Adiantum 



cc. Pinnae toothed on both margins, oblong in outline... 5. Pteris 

 BBB. Sori covered with a distinct scale-like indusium. 



c. Shape of sori oblong 6. Asplenium 



cc. Shape circular. 



D. Indusium circular-peltate, without a sinus 7. Polystichum 



DD. Indusium reniform, or if circular with a narrow 



sinus 8. Aspidium 



1. OSMUNDA. FLOWERING FERN. 



Strong ferns from stout creeping rootstocks, with large, pinnate fronds: 

 sporangia covered with interwoven ridges, but wanting the elastic ring of 

 most ferns. Inhabitants of bogs and wet woods. 



O. regalis, Linn. Royal fern. Top of the frond contracted into a fruit- 

 ing panicle: frond 2-pin- 

 nate, the pinnae oblong, ob- 

 tuse, and nearly entire. 



O. Claytoniana, Linn. 

 Fig. 479. Two to four pairs 

 of pinnae near the middle 

 of the frond contracted into 

 fruit-bearing parts: pinnae 

 linear-lanceolate and acute, 

 deeply lobed. 



O. cinnamdmea, Linn. 

 479. Osmunda Claytoniana (left). Osmunda Cinnamon fern , Fig . 479. 

 cinnamomea. 



Some fronds entirely con- 

 tracted into fruiting parts, and these cinnamon colored (whence the ver- 

 nacular name): sterile form with the fronds much like those of O. Clay- 

 toniana in shape except more acute at top. 



2. ONOCLEA. SENSITIVE FERN. 



Mostly rather strong ferns, with broad sterile fronds and with the fertile 

 fronds rolled into hard contracted fruiting bodies, which remain after the 

 sterile leafy fronds have perished: sporangia with an elastic marginal ring 

 of cells. Bogs and old springy fields. 



