The veins and veinlets of the frond are very distinct, being marked by depressions in the upper surface in the living fronds, and visible as dark lines in the dried specimens. The veins fork near the midvein; the upper branch may be fertile at its tip; the lower branch is either simple, or forks a second, and perhaps a third time. All the veinlets are curved. On account of the venation Presl referred this plant to his section _Arthrobotrys_. The sori are close to the margin of the lobes, and vary from one to twelve to a lobe. They are very large and prominent, and have firm lead-colored orbicular-reniform indusia, which are slightly incurved round the edge, and depressed at the sinus. As the fronds mature the indusia become brownish. The spores are ovoid-reniform and have a narrow crenulate wing. WALKING-LEAF. PINNATIFID SPLEENWORT. [Illustration: ] CAMPTOSORUS RHIZOPHYLLUS, Link. Walking-Leaf. Camptosorus rhizophyllus:—Root-stock short, creeping or ascending; stalks tufted, slender, flaccid, green, but becoming brown near the base; fronds a few inches to a foot long, sub-coriaceous, evergreen, smooth, gradually narrowed from a deeply cordate and auricled base to a long and very slender prolongation, decumbent and often rooting at the end; veins reticulated near the midrib, and having free apices along the margin; sori elongated, variously placed on either side of the veins, often face to face in pairs, or extending around the upper part of the meshes; indusium delicate. _Camptosorus rhizophyllus_, Link, Hort. Berol., ii., p. 69; Fil. Sp. Hort. Berol., p. 83.—Presl, Tent. Pterid., p. 121, t. 4, fig. 8.—Hooker, Gen. Fil., t. 57, C; Fil. Exot., t. 85.—Gray, Manual.—Darlington, Flora Cestr., ed. iii., p. 393.—Mettenius, Fil. Hort. Lips., p. 67, t. 5, fig. 6. _Asplenium rhizophyllum_, Linnæus, Sp. Pl., p. 1536.—Swartz, Syn. Fil., p. 74.—Willdenow, Sp. Pl., v., p. 305.—Michaux, Fl. Bor. Am., ii., p. 264.—Bigelow, Fl. Boston. _Antigramma rhizophylla_, J. Smith, in Hook. Journ. Bot., iv., p. 176; Ferns, British and Foreign, p. 226.—Torrey, Fl. New York, ii., p. 494, t. 159 (_Asplenium_). _Scolopendrium rhizophyllum_, Endlicher, Gen. Pl., Suppl. i., p. 1348.—Hooker, Sp. Fil., iv., p. 4.—Hooker & Baker, Syn. Fil., p. 248. Hab.—On mossy rocks, especially limestone. Not uncommon from Canada to Virginia and Alabama, and westward to Wisconsin and Kansas. It occurs in many places in Western New England, but is rare to the east. It has lately been found a few miles from Boston; but there is a doubt whether the station is truly natural.