32 Our Native Ferns. 



Allosorus includes coriaceous species having wide indusia, 

 while Platyloma includes species similar in texture but with ex- 

 tremely narrow indusia and broad segments. 



44. Ceratopteris is an anomalous genus having a few sori 

 arranged on two or three veins parallel to the midvein and cov- 

 ered by the broadly reflexed margin of the frond. 



45. Lomaria (Fig. 8) stands inter- 

 mediate between those genera in which 

 there is an indusium formed of the revo- 

 lute margin of the frond and those in 

 which the indusium is remote from the 

 margin. Our single species has dimor- 

 phous fronds, free veins and the fructifi- 

 cation in a broad band next the midvein, 

 covered by a continuous and distinctly 

 Fig. 8. Lomaria spicant, intramarginal indusium. This genus 

 Dcsv. Enlarged section of the ^^^^, resembles the next in general 



contracted fertile pinna show- . . - ..... 



ing intramarginal indusium. habit and IS sometimes united with It. 

 (Original.) 46. Blechnum. — In this genus the sori 



are linear and near the midvein, and are covered by a membranous 

 indusium which is fixed at its outer margin, bursting at its inner 

 margin when the sporangia are mature. A single representative 

 is found within our limits. 



47. Woodwardia. — Three species of chain-ferns occur within 

 our limits, and each represents a distinct section based on the 

 methods of venation. All have oblong or linear sori more or less 

 sunken in the frond, covered by special lid-like indusia bursting 

 at their inner margins, and arranged in chain-like rows near the 

 midvein thus giving the popular name to the genus. 



EuwooDWARDiA has uniform fronds and veins forming at least 

 one series of areolae between the sori and the margin. 



Anchistea has also uniform fronds but with free veins from 

 the sori to the margin, while Lorinseria has dimorphous fronds 

 and the veins everywhere uniting to form areolae, as in the sensi- 

 tive-fern (Onoc/ea sensibilis). 



48. Asplenium. — The numerous species of spleenworts are 

 closely related to each other in their methods of fructification but 

 differ widel^in the form, texture and cutting of their fronds. The 

 sori are placed on the upper side of an oblique vein (sometimes 

 crossing it in Athyrium) and covered by an indusium of the same 

 shape attached by its edge to the fruiting vein and opening toward 



