. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. 28 Out Native Ferns. Fig. 8. Scolopendrium vulgare, Sm- Section of frond showing venation and fructification. (Original.) 54. Scolopendrium (Fig. 8) bears the linear sori in pairs, one from the upper side of a veinlet and its mate from the lower side of the next. The indusia are at- tached by their edges to the veins, and folding toward each other appear like a double indu- sium covering a single sorus. The veins extend nearly at right- angles to the midvein, are free and usu
. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. 28 Out Native Ferns. Fig. 8. Scolopendrium vulgare, Sm- Section of frond showing venation and fructification. (Original.) 54. Scolopendrium (Fig. 8) bears the linear sori in pairs, one from the upper side of a veinlet and its mate from the lower side of the next. The indusia are at- tached by their edges to the veins, and folding toward each other appear like a double indu- sium covering a single sorus. The veins extend nearly at right- angles to the midvein, are free and usually forked. 55. Camptosorus.—The walk- ing-leaf has oblong or linear in- dusiate sori, which are irregu- larly scattered and borne partly on veins parallel to the midvein, and partly on those that are oblique. Those near the midvein are single, those toward the margin are often approximate in pairs and often form crooked lines. The veins are everywhere copiously reticulated. 56. Phegopteris.—In this genus the sori are round and naked as in Polypodium with which this genus is sometimes united. The sporangia spring from the back of the veins instead of the apex as in the latter genus and the veins are free. 57. Aspidium is largely represented in our limits by two well marked sections which are sometimes regarded as distinct genera, and two others with characters scarcely less distinct containing each a single species. In all the sori are roundish and borne on the back of the veins or rarely at their apex. In Nephrodium the indusium is cordato-reniform or orbicular with a narrow sinus. This at first covers the sorus and is attached by its margin, but later bursts away at the margin but remains attached at the sinus. In some species in this section the indusium becomes shriveled before the fruit matures and in this condition might be mistaken for a non-indusiate species (Fig. 9). In PoLYSTiCHUM the indusium is orbicular and peltate being fixed by the centre; the veins are free
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