78 OUR NATIVE FERNS AND THEIR ALLIES. 



tinct, clothed when young with ferruginous tomentum ; sterile 

 fronds smooth when mature, the pinnae bearing a tuft of tomen- 

 tum at the base beneath, lanceolate, cut into broadly oblong, 

 obtuse divisions ; fertile fronds contracted, bipinnate, with cin- 

 namon-colored sporangia. In var.frondosa Gray, some of the 

 fronds are sterile below, and sparsely fertile at the summit. 

 {O. Claytoniana Conrad.) New England and Wisconsin to 

 Florida. 



Family 5. CERATOPTERIDACE^E Underw. 



Plant body a short succulent stem with copious aquatic 

 roots bearing a rosette of succulent leaves of two sorts. Spo- 

 rangia irregularly scattered, sessile, with a broad ring or often 

 devoid of one altogether. The family is represented by a single 

 gdiius and species. 



I. CERATOPTERIS Brong. Floating-fern. 



Sori placed on two or three veins which run down the frond 

 longitudinally, nearly parallel with both the edge and midrib. 

 Sporangia scattered on the receptacles, sessile, subglobose, 

 with a complete, partial, or obsolete ring. Indusia formed of 

 the refiexed margins of the frond, those of opposite sides meet- 

 ing at the midrib. Name from Gr. Kepa.'i, horn, and Tirepii, a 

 fern. Contains a single tropical species. 



I. C. thaliotroides (L.) Brong. Stipes tufted, inflated, 

 filled with large air-cells ; fronds succulent in texture, the 

 sterile ones floating in quiet water, simple or slightly divided 

 when young, bi — tripinnate when mature ; fertile ones bi — ^tri- 

 pinnate ; ultimate segments pod-like. Southern Florida. 



Family 6. POLYPODIACE/E Presl. 



Plant body consisting of a creeping or erect stem (root- 

 stock) bearing scattered or clustered leaves (fronds). Spo- 

 rangia borne on the back or margin of the leaf in lines or 

 rounded masses (sori), stalked, provided with a vertical elastic 

 ring, breaking open transversely at maturity. Sori either naked 



