Part 4

Description:—Professor Robinson has remarked of this species:—“This comes nearer being a tree fern than any other of our species; the caudex, covered by the bases of fronds of previous seasons, sometimes resting on bare rocks for four or five inches without roots or fronds.” The root-stock is much like that of _A. Filix-mas_, being very stout-closely covered with persistent stalk-bases and very chaffy. The chaff really grows mainly on the bases of the stalks, or covers the closely coiled buds which crown the root-stock. It is composed of shining ferruginous-brown thin lanceolate acuminate scales fully an inch in length, and destitute of a thickened midnerve. The fronds grow in elegant crowns from the apex of the root-stock, some six or eight or perhaps ten to a plant. The stalks vary in length, but are seldom more than a foot long. They are rather stout, round, but with a slight furrow in front, commonly reddish-brown in color, fading when dry to straw-color, and contain five or seven roundish fibro-vascular bundles, of which the two anterior ones are largest, and the next two the smallest.

The outline of the fronds is ovate-lanceolate, varying to oblong-lanceolate. The frond is commonly not quite so wide at the base as in the middle, though in small specimens the base is often the widest. The texture is thicker than in any other of our Wood-ferns, and the fronds are fairly evergreen, not withering until the next year’s fronds begin to uncoil. In cutting, the fronds vary from pinnate, with pinnatifid pinnæ and short nearly entire lobes, to twice pinnate, with pinnately-lobed segments. In the example selected for our plate the pinnules are oblong, obtuse and crenulate, or at most, crenately-toothed. Other, and perhaps no larger, fronds will have most of the pinnules twice or even thrice as long as these, ovate-lanceolate and pointed, narrowed to a sub-cordate and obscurely-stalked base, and deeply pinnately-lobed. This is var. _elegans_ of Professor Robinson. Professor Lawson has a var. _Traillæ_, which has “very large bipinnate fronds, all the pinnules pinnatifid.” A very common form noticed by Mr. L. M. Underwood in Bulletin of the Torrey Botanical Club, has fronds only four or five inches long, the lower pinnæ only pinnatifid and the upper ones lobed, the sori mostly solitary on the lobes.

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.

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.

Description.—The walking-leaf is usually found in patches of considerable extent. It seems to prefer mossy calcareous rocks, and the finest specimens are usually firmly rooted in the crevices. In Cheshire, Connecticut, it grows freely on moist cliffs of sandstone bordering a deep ravine; and in Orange, in the same State, it is found on scattered ledges of serpentine. The root-stock is very short, but creeping: it bears a few dark-fuscous scales, and is covered with the remains of decayed stalks. A few fronds grow from the end of the root-stock, and are supported on slender herbaceous stems a few inches long. A transverse section of the lower part of the stalk is semicircular, and shows a very slender triangular central thread of dark sclerenchyma, with two somewhat roundish fibro-vascular bundles close beneath or behind it. A section higher up shows that the stalk is there narrowly winged on each side, and the two fibro-vascular bundles have coalesced into one of a roundish-triangular shape. The frond is long and narrow, and rarely rises erect, but usually is decumbent or reclined in position.

The wings of the stalk widen out into a wedge-shaped base, which is sunken in a sinus between two basal auricles of the frond. These auricles are scantily developed in small fronds; but in larger ones they are more or less prominent, making the base of the frond either cordate or hastate. In specimens from Cheshire, Connecticut, and in some from Indiana, the auricles are drawn out into slender points, in one instance fully four inches long. The fronds are deep-green in color, and sub-coriaceous in texture. The fronds of mature plants are from six to twelve, or even fifteen, inches long; and their greatest width, measured just above the auricles, is about one-twelfth of the length, or from six to fifteen lines. The midrib is a little paler than the rest of the frond, and is rather prominent on the under surface. The margin of the frond is gently undulating or entire, rarely incised.[2] The upper part of the frond is scarcely wider than the stalk, and commonly produces a proliferous bud at the apex, where it very frequently takes root, and develops a new plant. In this way a single plant in a favorable position will become a whole colony in a few years’ time.

The venation is peculiar, and the disposition of the sori depends mainly on the peculiarities of the venation. Dr. Endlicher’s description of them is so clear, that it is well to repeat it here: “Veins anastomosing [i.e., reticulating] in two series of hexagonal areoles [meshes], the angles of the marginal areoles sending out free, simple or forked, veinlets. Sori linear, solitary in the costal areoles [those nearest the midrib] and on the marginal veinlets: the indusium of the latter free toward the margin of the frond; of the former, toward the costa. In the areoles of the second series the sori are opposite: the indusium of the lower one free toward the costa; of the other, in the opposite direction.” To this it may be added, that in some of the areoles the two sori meet and are confluent at the outer angle of the areole; and in this case the two indusia are sometimes, though not always, united into one. The indusia of the areoles next the midrib are also often bent at an angle, and the two portions plainly united. It was from this condition of some of the sori that the genus was named _Camptosorus_ (bent fruit-dot); and it is only on this peculiarity that the genus can be kept separate.

The indusium is thin and delicate, composed of sinuous-margined cellules, and is more or less wavy along the free edge. The spores are ovoid, and have a crenated pellucid wing-like margin.

Sir W. J. Hooker referred the _Camptosorus_, together with the species of _Antigramma_, and the very peculiar Mexican fern _Schaffneria_, to the genus _Scolopendrium_; making the distinctive character of the genus to rest on the sori being “in pairs, opposite to each other, one originating on the superior side of a veinlet, the other on the inferior side of the opposite veinlet or branch.” In this he was essentially anticipated twenty years by Dr. Endlicher; to whom, however, _Schaffneria_ was unknown.

It is by no means impossible that future botanists will refer all these species to the old Linnæan genus _Asplenium_; for it is now pretty generally admitted that differences in venation do not constitute valid generic distinctions, and a radicant bud on the frond is common in many undeniably genuine _Asplenia_: and since _Diplazium_, with double involucres placed back to back on the same vein, is inseparable from _Asplenium_, it is by no means impossible that _Scolopendrium_ and _Camptosorus_ should be thought to have no better claim to rank as genera.

Probably the earliest notice of the walking-leaf is in Ray’s “Historia Plantarum,” vol. ii., p. 1927, published in 1688. It is there called “Phyllitis parva saxatilis per summitates folii prolifera.” Other early accounts may be found in the “Species Plantarum” of Linnæus and of Willdenow, and in the second edition of Gronovius’s “Flora Virginica.” In the latter work it may be seen that Gov. Colden long ago described the auricles as being “also often acuminate.”

A second species, with membranaceous fronds acute at the base (C. Sibiricus), occurs in Northern Asia, but is apparently very rare.

ASPLENIUM PINNATIFIDUM, Nuttall. Pinnatifid Spleenwort.

Asplenium pinnatifidum:—Root-stock short, creeping, branched; stalks numerous, clustered, brownish near the base, green higher up; fronds six to nine inches high, herbaceous or sub-coriaceous, mostly erect, lanceolate-acuminate from a broad and sub-hastate base, pinnatifid; lower lobes roundish-ovate or rarely caudate, sometimes distinct, the margin crenated, the upper ones gradually smaller and more and more adnate to the winged midrib; the uppermost very short, and passing into the sinuous-margined long acumination of the frond; veins dichotomous or sub-pinnate and forking, free; sori few on the lower lobes, solitary on the uppermost, those next the midrib occasionally diplazioid.

_Asplenium pinnatifidum_, Nuttall, Genera of N. Amer. Plants, ii., p. 251.—Kunze, in Sill. Journ., July, 1848, p. 85.—Gray, Manual.—Eaton, in Chapman’s Flora of Southern U. S., p. 592.—Hooker, Icones Plantarum, t. 927; Sp. Fil., iii., p. 91.—Mettenius, Fil. Hort. Lips., p. 72, t. 10, figs. 1, 2; Asplenium, p. 126.—Hooker & Baker, Syn. Fil., p. 194.

_Asplenium rhizophyllum_, var. _pinnatifidum_, Muhlenberg, Catalogus Plant. Am. Sept., ed. ii., p. 102.—Barton, Compendium Floræ Philad., ii., p. 210.—Eaton,[3] Manual of Botany, ed. iii., p. 188, etc.—Torrey, Compendium, p. 383.

Hab.—Discovered by Thomas Nuttall in crevices of rocks along the Schuylkill River, near Philadelphia; also found along the Wissahickon Creek in the same vicinity. Lancaster County, Pennsylvania, Prof. Thomas C. Porter. On moist cliffs of sandstone in the Cumberland Mountains, East Tennessee, Prof. F. H. Bradley. Hancock County, Alabama, Hon. T. M. Peters. Mine-la-Motte, Southern Missouri, on sandstone rocks, Dr. Engelmann.

Description.—The root-stocks of this little fern are creeping, branched and often entangled, and chaffy with narrow lance-acuminate dark-fuscous scales. The cellular structure of these scales is similar to that of the scales of _A. ebeneum_, the cells being oblong-rectangular, and arranged in straight longitudinal rows. The stalks are from two to four inches long, and slightly chaffy when young: they are brown and shining at the base, but green higher up, except that a narrow line of brown is continued up the under side of the stalk nearly or quite to the base of the frond. A section made near the lower extremity of the stalk is nearly semicircular, and discloses two roundish fibro-vascular bundles side by side near the middle, and a minute thread of sclerenchyma, or hard dark tissue, on the inner side of each bundle. A section just below the frond shows the two fibro-vascular bundles united into one, and the angles of the stalk slightly extended, forming very narrow wing-like borders. The minute inner filaments of sclerenchyma are never continued far up the stalk, and are sometimes wanting altogether.

The frond is from three to six inches long, and usually half an inch to an inch broad at the base, from which the general outline tapers to a long and slender point, not so long as the prolongation of the walking-leaf, and very rarely, if ever, rooting at the apex.[4] The fronds are mostly erect, sub-coriaceous or firmly membranaceous, smooth above, but with a few minute setulose scales beneath, deeply pinnatifid in the lower and middle portion, and sinuately lobed above, the long terminal portion undulate on the margins. The midrib is broad and well defined: it is winged throughout its length; the wing narrow at the base of the frond, but constantly widening upwards.

The lobes are irregularly roundish-ovate, sinuate, crenate or slightly toothed; the lowest ones occasionally drawn out into an acuminate point an inch long. Most of the lobes are attached to the wing of the midrib by a broad base: the lower ones sometimes have a short stalk.

The veins are everywhere free: in the lower lobes, if these are acuminate, the veins are pinnately branched from a mid-vein; elsewhere they are forked or dichotomous. The sori are mostly single, though here and there one will be diplazioid,—most commonly the lowest one on the superior side of the lobe. The indusia are very delicate; and the free edge is directed toward the middle of the lobe, excepting the indusia of the sori nearest the midrib, and these open toward the midrib. The sori are usually very full of sporangia, and, when ripe, nearly cover the back of the frond: even the narrow acumination bears a sorus at each undulation of the margin. Spores ovoid-bean-shaped, with reticulating ridges and an irregular winged border.

This is now admitted by all pteridologists to be a distinct species; though it was formerly confounded with the _Camptosorus_, from which it is clearly distinguished by the free veins, the mostly single indusia, and the usual absence of a proliferous bud at the apex of the frond. Some of the less compound and more attenuated forms of _A. montanum_ come much nearer to it; but in its simplest form this other species always has the fronds fairly pinnate, and its more compound forms resemble the _A. pinnatifidum_ very little.

I take occasion to express my thanks to Hon. Thomas M. Peters of Moulton, Alabama, who has sent me abundant and fine specimens of this fern and of other rare species which are found in the northern part of Alabama.

SENSITIVE FERN.

ONOCLEA SENSIBILIS, Linnæus. Sensitive Fern.

Onoclea sensibilis:—Root-stock creeping, elongated; stalks scattered, nearly chaffless, a few inches to over a foot high; fronds dimorphous; sterile ones triangular-ovate, foliaceous, smooth, quickly withering when plucked, deeply pinnatifid into several oblong-lanceolate entire or sinuate or sinuately pinnatifid segments, the lowest pair sometimes distinct, the rest connected by a wing which widens upwards; the veins reticulated and forming narrow paracostal areoles, and, outside of these, copious oblong or hexagonal meshes; fertile fronds shorter, contracted, rigid, closely bipinnate; the pinnules rolled up into berry-like bodies; veins free, simple or forked, soriferous on the back; sporangia borne on an elevated receptacle, half surrounded by a very delicate somewhat hood-like indusium attached at the base of the receptacle.

_Onoclea sensibilis_, Linnæus, Sp. Pl., p. 1517.—Michaux, Fl. Bor.-Am., ii., p. 272.—Swartz, Syn. Fil., p. 110.—Schkuhr, Krypt. Gew., p. 95, t. 102.—Willdenow, Sp. Pl., v., p. 287.—Pursh, Fl. Am. Sept., ii., p. 665.—Hooker, Gen. Fil., t. lxxxii; Fl. Bor.-Am., ii., p. 262; Sp. Fil., iii., p. 160.—Torrey, Fl. New York, ii., p. 499.—Gray, Manual, ed. i., p. 457; ed. ii., p. 599, t. xii; ed. v., p. 668, t. xviii; Botany of Japan, in Mem. Amer. Acad. (n. s.) vi., p. 421.—Mettenius, Fil. Hort. Lips., p. 97.—Maximowicz, Prim. Fl. Amur., p. 337.—Eaton, in Chapman’s Flora, p. 596.—Hooker & Baker, Syn. Fil., p. 46.—Miquel, Prolus. Fl. Jap., in Ann. Mus. Bot. Lugd.-Batav., iii., p. 179.—Milde, Fil. Eur. et Atlant., p. 157.—Redfield, in Bulletin of Torrey Botan. Club, vi., p. 4.—Williamson, Ferns of Kentucky, p. 109, t. xli; Fern-Etchings, t. xlv.

_Onoclea obtusilobata_, Schkuhr, Krypt. Gew., p. 95, t. 103.—Pursh, Fl. Am. Sept., ii., p. 665.

_Onoclea obtusiloba_, Link, Fil. Hort. Lips., p. 37.

_Osmunda frondibus pinnatis foliolis superioribus basi coadunatis, omnibus lanceolatis, pinnato-sinuatis_, Linnæus, Hort. Cliff., p. 472.—Gronovius, Fl. Virginica, p. 196; ed. ii., p, 163.—(Other ancient names are repeated by Linnæus and Willdenow.)

Hab.—Wet meadows and thickets, from New Brunswick to the Saskatchewan, extending southward through Dacotah, Kansas, and Arkansas to Louisiana, and eastward to St. Augustine, Florida, one of our commonest and most abundant ferns, often occupying large portions of land to the partial exclusion of other plants. Not found in western America or in Europe, but occurring in Japan, Mantchooria and eastern Siberia.

Description:—The root-stock is about one-third of an inch thick, and irregularly roundish in section. It creeps widely below the surface of the ground, rooting freely and often forking, so that in cultivation it is very difficult to confine the plant to one spot. The root-stock contains six or eight roundish or flattened fibro-vascular bundles arranged in a circle near the outer surface. It bears no chaff. The stalks are scattered along its length, the apex being covered with the thickened stalk-bases of next year’s fronds, and the stalks for the present year rising a few inches back of the apex.

The fronds are truly dimorphous, the fertile ones being so unlike the sterile, that no one who is unacquainted with the plant would suppose they had anything to do with each other.

The sterile fronds vary in length from one or two inches to fifteen or eighteen, and are supported on stalks usually rather longer still, so that, while the smallest plants may be concealed in the grass, the tallest ones are often fully three feet high. The bases of the stalks are flattened, discolored and very sparingly chaffy; the upper part is green in the living plant, brownish-stramineous when dried, smooth and naked, rounded at the back, and slightly furrowed in front. It contains two obliquely-placed strap-shaped fibro-vascular bundles, which unite below the base of the frond and form one having a U-shaped section. The outline of the sterile fronds is triangular or triangular-ovate. The midrib is winged, either from the very base, or from the second pair of segments; the wing at its lower extremity very narrow, but gradually widening towards the apex, so that its greatest width is but little less than that of the terminal segment. The number of segments in the smallest fronds is two or three on each side; in the largest fronds twelve or thirteen on each side. The lowest segments are rather more than half as long as the whole frond; the next segments usually a little smaller, but sometimes a little longer than the first pair, and the remaining ones rapidly decreasing. The segments are broadly lanceolate or oblong-lanceolate, narrowed at the base, especially the lower ones, and either rounded or sub-acute at the apex. The sinuses between them are rounded, and are gradually narrowed towards the apex of the frond. The segments are very minutely serrulate on the edges; the smallest ones otherwise entire, and the larger ones either with sinuous margins or, in large fronds, deeply sinuous-pinnatifid. The texture is herbaceous, the surfaces perfectly smooth, the color of the upper surface grass-green, of the lower surface paler and slightly glaucescent. The fronds wilt very soon after plucking them, and in wilting there is a slight disposition to fold the segments together, face to face, for which reason the plant has received the name of “Sensitive-Fern.” The first frost of autumn destroys the sterile fronds; and a late frost in May or June does the same. The midribs are prominent, and the veins conspicuous; the latter being copiously reticulated into areoles which enclose no free veinlets. Along the sides of the midribs and midveins are very long and narrow areoles, and outside of these are obliquely-placed oblong areoles in several irregular rows.

The fertile fronds are not very common, and a young botanist may search in vain for them for a long time. They stand only about half as high as the sterile fronds, and are very rigid. They are nearly black in color: in winter they dry up, but remain erect through the next summer, so that a fruiting plant often has fertile fronds standing of two years’ growth. The frond is only a few (usually four to six) inches long, and consists of from four to ten pairs of appressed fleshy or cartilaginous pinnæ, which are divided into a double row of sub-globose bead-like segments or pinnules; the whole looking like a small and narrow but dense cluster of diminutive grapes. Each pinnule has its edges so much recurved that the whole forms a sort of pouch, apparently filled with sporangia.

Mr. Faxon has made a careful study of the sori, and has very kindly furnished the account given below.[5]

The articulations of the sporangia are said by Fée to be twenty-eight to thirty-two, and more numerous than in any other fern. I have counted only thirty at most, and more frequently only twenty-eight. The spores are ovoid and very dark-colored.