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Rhodora/006/A New Hybrid Fern from Vermont

< Rhodora‎ | 006
Margaret Slosson.

Dryopteris Pittsfordensis, hyb. nov. — Mature sporophyte large, 1½–2, or more feet tall, resembling that of D. spinulosa dilatala, the young fronds like those of D. marginalis with the lowermost pair of pinnae enlarged, partially evergreen, the sporophylls withering in late autumn.

Rootstock decumbent, as in D. spinulosa, between which and D. marginalis the plant is a probable hybrid.   Fronds fasciculate, crosiers densely clothed with pale brown scales; stipes 6–12 inches long, usually about one-third the length of the frond, stramineous, browning with age, especially below, deeply furrowed along the face, and clothed with a mixture of broad, narrowly ovate, and linear-lanceolate acuminate entire or lacerated brown scales, darkest below and often with blackish brown centres, paler and transparent above, becoming chaffy along the strongly grooved and winged rachises; fibro-vascular bundles 3-5 or 7.  Laminae 10-20 or more inches long, 6-10 inches broad, oblong or ovate lanceolate, or triangularovate with long acuminate apices, broadest just below the middle, bipinnate or, in the largest forms, tripinnate, at least below; pinnae mostly ovate or oblong lanceolate, long-acuminate, the lowermost pair much the broadest and irregularly deltoid, the superior pinnules much the longest, lobes irregularly spinulose or sharply toothed; texture subcoriaceous, softly downy in the young fronds, and wrinkled on the face from the deep furrows of the midribs and veins; sori elevated, submarginal, reniform, indusia coriaceous; veins pinnately branched and forked.

Syn. Nephrodium Pittsfordense Davenport, in litt.

Fig 1 Dryopteris pittsfordensis.png Fig 2 Dryopteris spinulosa intermedia.png Fig 3 Dryopteris marginalis.png
Fig. 1, portion of a pinna of Dryopteris Pittsfordensis, × 1½. Fig. 2, part of a pinna of D. spinulosa intermedia, × 1½. Fig. 3, part of a pinna of D. marginalis, × 1½.

The special characters of this plant lie in the long-acuminated outline of the fronds and pinnae, the submarginal elevated sori and coriaceous indusia, and the occasional presence on the older stipes of large deeply lobed or lacerated appressed scales with a broad dark base and the exterior lobe greatly elongated.   The scales of the stipes are for the most part attached at the base by a well rounded sinus with either entire or ciliated margins; the smaller ones much like those on some of the Polypodiums, as for example, P. polypodioides.

In the subcoriaceous texture, and to some extent in the coloring, of the fronds, and in the conspicuous submarginal elevated sori appearing almost cork-like in age, the plant resembles D. marginalis.   The toothed margins of the fronds, on the other hand, suggest D. sptnulosa.  Both at first sight and on close examination the hybrid character of the plant appears unquestionable.

I first found this plant in 1895, growing among stones by a roadside in Pittsford, Rutland County, Vermont. The specimens formed a large clump.   Nearby grew D. marginalis and a form of D. spinulosa.

In 1901 the hybrid clump was transplanted to Mr. George E. Davenport's garden in Medford, Massachusetts, where it has remained since.   It has produced mostly smaller fronds in the new location than in the old, but apparently has lost none of its peculiar characteristics at any time.

Type specimens are in the herbarium of the New York Botanical Garden.

I am greatly indebted to Mr. Davenport for his kind assistance in he study of this fern.

Note by Mr. Davenport. — Since Miss Slosson's fern was transplanted to my garden in 1901 it has increased to five plants from young crowns growing out from the main rootstalk.   One of the new plants was sent to Miss Slosson and another has been reserved for the Botanical Garden at Cambridge.  During the past two seasons I have pressed all available fronds from the original plant and specimens of these will be deposited in the Gray Herbarium, the Herbarium of the New England Botanical Club, and the Davenport Herbarium of the Massachusetts Horticultural Society.  In 1893 Mr. Raynal Dodge collected some specimens which he regarded as of hybrid origin between Nephrodiutn spinulosum and N. marginale.  These I have had under examination for some time, but in the absence of the rootstalk, and other necessary data, I have not been able to satisfy myself as to their exact status.  They differ greatly, however, from Miss Slosson's fern. — G. E. D.