22 



POLYPODIACEAE. 



VOL. I. 



12. Dryopteris intermedia (Muhl.) Gray. American Shield- fern. Fig. 48. 



Polypodium intermedium Muhl. ; Willd. Sp. PI. 5 : 262. 



1810. 



Aspidium americanum Davenp. Am. Nat. 12: 714. 1878. 

 Dryopteris spinulosa var. intermedia Underw. Nat. Ferns, 



ed. 4, 1 1 6. 1893. 



Rootstock creeping. Leaves equal, spreading in a 

 complete crown; stipes 4'-i4' long, with light brownish 

 or darker-centered scales ; blades similar in size and 

 shape to those of D. spinulosa, glandular-pubescent 

 when young ; pinnae usually at right angles to the rachis, 

 the lower ones at least pinnate, unequally lanceolate to 

 ovate-lanceolate; the upper ones lanceolate to oblong, 

 acuminate ; pinnules convex, oblong or lanceolate, acute, 

 the largest not decurrent, pinnately divided, nearly at 

 right angles ; segments dentate, usually straight ; sori sub- 

 marginal, subterminal; indusia glandular. 



In moist woods, Newfoundland to Wisconsin, south to 

 North Carolina and Tennessee. Known only from eastern 

 North America. Called also Common Wood-fern. 



13. Dryopteris Boottii (Tuckerm.) Underw. 

 Boott's Shield-fern. Fig. 49. 



Rootstock stout, ascending. Stipes 8'-i2' long, 

 covered below with thin pale-brown scales ; blade 

 of fertile leaves elongate-oblong or lanceolate, acu- 

 minate, slightly narrowed toward the base, firm, 

 bipinnate, or 3-pinnatifid, i-2J long, 3'-5' wide, the 

 sterile ones commonly shorter and less divided; 

 middle and upper pinnae lanceolate with a broad 

 base, acuminate, those below unequally deltoid- 

 lanceolate, the lowest elongate-triangular; pinnules 

 oblong-ovate, constricted at the base, the lower ones 

 nearly sessile, often pinnatifid, those above adnate 

 and slightly decurrent upon the narrowly winged 

 rachis, serrate, the margins spinulose throughout; 

 sori numerous, distinct, medial or nearer the mid- 

 vein ; indusia orbicular-reniform, glandular. 



In low woods and wet thickets. Nova Scotia to Min- 

 nesota, south to Virginia and West Virginia. July-Sept. 



Several American writers regard D. Boottii as a natural hybrid between D. cristata and D. 

 intermedia. Other supposed hybrids have recently been described, which have been confused 

 either with D. Boottii or with species of which they were regarded as aberrant forms. The 

 characters of these are such as to support strongly the hybridity hypothesis. They should be 

 sought in localities exceptionally favorable to a mingling of the supposed parent forms. A list of 

 these, including D. Boottii, follows : 



Dryopteris Clintoniana x Goldiana Dowell, Bull. Torrey Club 35: 137. 1908. 



Dryopteris Goldiana celsa Palmer, Proc. Biol. Soc. Wash. 13: 65. 1899. 

 Dryopteris Clintoniana x intermedia Dowell, Bull. Torrey Club 35: 136. 1908. 

 Dryopteris Clintoniana X marginalis Slosson, Bull. Torrey Club 37: 202. 1910. 

 Dryopteris Clintoniana X spinulosa Benedict, Bull. Torrey Club 36: 45. 1909. 

 Dryopteris cristata x Goldiana Benedict, Bull. Torrey Club 36: 47. 1909. 

 Dryopteris cristata x intermedia Dowell. Bull. Torrey Club 35: 136. 1908. 



Aspidium Boottii Tuckerm. Hovey's Mag. 9: 145. 1843. 



Aspidium spinulosum var. Boottii D. C. Eaton in A. Gray, Man., ed. 5, 665. 1867. 



Dryopteris Boottii Underw. Nat. Ferns, ed. 4, 117. 1893. 



Dryopteris cristata X spinulosa intermedia Slosson, Fern Bull. 16 : 97. 1908. 

 Dryopteris cristata X marginalis Davenp. Bot. Gaz. 19: 497. 1894, as syn. 



Aspidium cristatum X marginale Davenp. Bot. Gaz. 19: 494. 1894. 

 Dryopteris cristata x spinulosa (Milde) C. Chr. Ind. Fil. 259. 1905- 



Aspidium cristatum X spinulosum Milde, Nov. Act. Acad. Leop.-Carol. 26: 533. 1856. 

 Dryopteris Goldiana x intermedia Dowell, Bull. Torrey Club 35: 138. 1908. 

 Dryopteris Goldiana x marginalis Dowell, Bull. Torrey Club 35: 139. 1908. 

 Dryopteris Goldiana X spinulosa Benedict, Bull. Torrey Club 36: 47. 1909. 

 Dryopteris intermedia x marginalis Benedict, Bull. Torrey Club 36: 48. 1909. 

 Dryopteris marginalis x spinulosa Slosson, Fern Bull. 16: 99. 1908. 



Dryopteris pittsfordensis Slosson, Rhodora 6: 75. 1904. 



Nephrodium pittsfordense Davenp. Rhodora 6: 76. 1904, as syn. 



Aspidium spinulosum X marginale Eggleston, Rhodora 6: 138. 1904. 



