. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. 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
. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. 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-
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