DIDYMOCHLiENA.

5

the description of the Russian botanists. Linnaeus had 'probably this plant inview, when he gives his Aspl. rhizophyllum as a native of Siberia .

Subord. VIII.—ASPIDIACE E, Pr.

Sori dorsal, subglobose, rarely elliptical. Involucre superior,orbicular and fixed by the centre (peltate), or cordate or reni-form and fixed by the sinus, or elliptical and attached by alongitudinal receptacle; the margins free all round or nearlyso.—Ferns very various in habit; veins free or variouslyanastomosing.

The genera I am disposed to admit under this Order are as follows 1. Didy-mochl^na. 2. Aspidium, mainly distinguished by its more or less orbicularpeltate involucres, with the following sections or subgenera ■. — § Polystichum,

§ Cycloditjm, § Cyrtomium, § Euaspidium, next to which I am disposed toplace § Sagenia. 3. Nephrodium, Rich, and Br., chiefly distinguished byits cordate or reniform involucre, fixed at the sinus. Subgenera. § Lastrea,with free veins. § Eunephrodium, with connivent veins, including Pleoc-nemia. 4. Nephroi.epis. 5. Oleandra. 6. Fady'enia. 8. Onoclea. It istrue a synopsis of their character is not to be given a few words; but theyappear to me to have sufficient marks of distinction natural or artificial.

1. Didymochl^na, Desv.

(Hook. Gen. Fil. tab. VIII.)

Sori dorsal, terminal on a veinlet, elliptical. Involucreelliptical, emarginate at the base, attached by a longitudinalreceptacle, free all round at the margin. Veins subflabellate,several times forked, free, the apices of the veinlets clavate.—Caudex erect, stout, arboreous. Fronds tufted, terminal,4-6 feet long, stipitate, erecto-patent, subcoriaceous, bipinnate.Pinnules f-1 inch long, obliquely rhomboid. Sori submarginalmostly on the superior half of the pinnule.

1. D. lunulata, Desv. in Mem. Soc. Linn. vi. p. 282.Hook. Gard. Ferns, pi. 17- D. sinuosa, Desv. l.c. p. 28.Mart. Ic. PI. Crypt . Bras . p. 95. t. 28 and 29. /. 1. Hook.Gen. Fil. t. 8. D. squamata, Desv. Journ. Bot. Appl. i. p. 5.t- 2- /. 4. D. truncatula, J. Sm. Gen. of Fer^,p. 84. D. di-midiata, Kunzein Linn/m, xviii. p. 122. Schk. Fil. Suppl. p.200. t. 84. Pappe and Raws. Syn. Fil. Afr. p. 15. Aspidiumtruncatulum, Sw. Syn. Fil. pp. 52 and 252. Willd. Sp. PI. v.p. 256. Aspid. squamatum, Willd. Sp. PI. v. p. 250. Mono-chlaena sinuosa, Gaudich. in Freyc. Voy. Bot. p. 340. t. 12./• 3. Diplazium pulcherrimum, Raddi, Fil. Bras . p. 42. t. 59.Lonchitis ramosa, etc., Plum. Fil. p. 43. t. 56.