(>() Dlf'KSONIA. 



to unite the several genera al)ove mentioned ; and thus, as it were, to re- 

 store the original genus Dicksonia, as understood l)y L'Heritier. It is true, 

 if we look at the majority of species of the Prttoreifl-group, there is a consi- 

 derable difference, Loth in habit and apparently in the structure of the in- 

 volucre, from the arborescent species of the Balanlinm-fxroup- but, in regard 

 to habit, all intermediate grades may be seen, and the difference of structure 

 in the involucre is more in appearance than in reality. In both cases the 

 involucre may be said to be double: there is a true and an accessory one ; 

 the true one, generally membranous, is situated near the margin, below a 

 small lobule of the frond, which latter is recurved, more or less changed in 

 texture, and united with the true one in a (/renter or less degree; in the first 

 case forming the cup-shaped or campanulate, generally entire, involucre of 

 Patania ; in the latter case the2-lipped or 2-valved involucre of Balantium 

 &c. In some instances, as in our D. Plumieri, our D. dubia {Davallia dubia, 

 Br.), the accessory and the true involucre are scarcely united, and then it is 

 difficult to distinguish the genus from some Davallia:, especially that group 

 called Microlepia by Presl. In short, it may be said that the proper invo- 

 lucre of Davallia united with the accessory one of Cheilanthes, go to form 

 that of Dicksonia. 



Subgen. I. Balantium. Involucre distinctly 2-ialved. Balantium, 

 Kaulf. Culcita, Pr. Leptopleuria, Pr. Cystodium, J. Sm. 



1. D. arhorescens, L'Heiit. ; arborescent, fronds bi-tripin- 

 nate coriaceous, pinnse oblong scarcely attenuated obtuse, 

 pinnules or segments ovate acute serrated decurrent upper 

 ones coadunate, fertile pinnules contracted, stipes rachis and 

 costa beneath clothed with ferruginous glandular wool. (Tab. 

 XXII. A.). HHerit. Sert. Anyl. p.^l. Wall. Cat. n. 64. 

 Dicksonia integra, Sw. Balantiiun arborescens, Hook. Gen. 

 Fil. I. c. B. auricomum, Kaulf. Ennm. Fil. p. 228, t.^\,f. 

 12. Presl. 



Hab. Island of St. Helena, Sir Jos. banks. Dr. Snlander, and various 

 travellers ; only near the highest summit of Diana's Peak, /. D. Hooker. — 

 Caudex 9 or 10 feet high, clothed with the bases of the old stalks of the 

 fronds and crowned at the summit with a horizontal tuft of dark rusty green 

 foliage. The fronds are peculiarly thick and coriaceous, tripinnate. Se- 

 condary pinnae numerous, closely arranged, oblong-lanceolate, pinnate in 

 the lower half, the rest coadunate. Pinnules and segments larger than in any 

 of the genus. Sori generally on much-contracted pinnules, very large and 

 conspicuous, copious. Clavate, glandular, articulated hairs are mixed with 

 the capsules. The woolly ferruginous hairs of the rachis are also jointed. 

 The sketch of the entire Fern here given (Tab. XXII), was made by Dr. J. 

 D. Hooker, on returning from the Antarctic voyage in H. M. S. Erebus. 

 He gathered also fine specimens of the fronds, and brought home living 

 plants to the Royal Botanic Gardens of Kew. 



2. D.antarclica, Labill.; arborescent, fronds supradecom- 

 ]50und elliptical coriaceous glabrous, idtimate pinnae oblong 

 or oblong-lanceolate all of them acuminated at the apex, pin- 

 nules and segments ovate ver}^ acute pungent inciso-serrate, 

 fertile ones pinnatifid scarcely altered, sori small, general ra- 

 chis scabrous. — Lnbill. Nov. Holl. v. ii. p. 100, t. 249. Br. 



