f 
226 BOTANY OF THE VOYAGE OF H.M.S. HXUALD, 
FILICES. 
{Aiicto7-e J. Smith.) 
In this enumeration, I have followed tlie arrangement publislied hy me in Hooker's ' Journal of 
Botany,' vol. iv. p. 4G et seq., except in such cases where later observations and altered views have rendered 
changes necessary. In my enumeration of the Ferns cultivated in the lioyal Botanic Gardens at Kew 
(Botanical Magazine, vol. Ixii., 1846) I arranged the species of Pohji^odiwn under four sections, charac- 
terized by the different modes in which the fronds are developed and attached to the axis of growth 
(vernation). The first of these sections contains Polypodium viiJgare, which, with its allies, presents a 
mode of growth (^uite different from that of those species constituting the other three sections ; the three 
latter I now consider as presenting only different modifications of another and more general mode of 
growth-; and although all the species of the four sections agree in the technical character oi Poly;podium, 
in having punctiform naked sori seated on free veins, yet the two different modes of growth found in the 
various species of Polypodium appear to me to be quite sufficient to warrant a separation of the species 
under distinct genera. I therefore restrict true Polypodium to those species having the same kind of 
vernation as Pohjpodium vttlyare. The genus may then be viewed as representing a natural group of Ferns 
having the following characters :— The fronds are developed from the sides of a special rhizome, which has 
its axis of growth always in advance of the nascent frond (excurrent) ; the fronds are produced from nodes 
more or less distant from each other, each node producing a single frond, which, after having arrived at 
maturity, separates by a special articulation formed between the node and the base of the stipes ; after the 
frond has fallen, the node remains in the form of a round, concave cicatrix, generally more or less elevated ; 
the rhizome is solid, fleshy, and brittle, varying from long and slender to more or less short and thick, and 
is always covered with scales, which, unless they are common to the whole frond, seldom extend upwards 
beyond the node. This mode of development, which I have termed Eremobrya, is peculiar to a conside- 
rable number of Polypodiecd, including genera both with free and anastomosing veins ; also a poi-tion of 
BavaUia, of which I). Canariensis may be viewed as the type, the whole forming a truly natural group 
of Ferns. The other mode of development to which I have alluded, and to which I have given the name 
of Desmoh-ya, is observable in a more numerous group of Ferns, bearing the following characters : — The 
fronds from a terminal axis, cither in a single alternate series, or in a fascicle forming a corona; each 
succeeding frond is produced on the interior side of the bases of the preceding fronds, the bases being 
united and adherent ; by the successive evolution of fronds a progressing accessory stem or eormus is 
formed, which varies in being decumbent or erect, short or more or less elongated, often assuming the as- 
pect of trees, or, creeping on or under the surface of the ground, frequently forming ceespitose tufts ; in 
those species producing their fronds in a single scries, the developing axis sometimes elongates before the 
evident evolution of the fronds, which are then more or less distant from each other, and by this mode of 
growth forming a creeping or scandent caudex, wliicli often assumes tlie character of a sarmentum, and 
then appears to agree with the mode of growth I have called Eremohrya^ hut it is readily distinguished by 
the epidermis and vascular structure of the stipes heing continuous and united, forming part of the deve- 
loping axis, and not being articulate as in Eremobrya. The various modifications of the structure obser- 
vable in the group Desmohrya often mark the limits of what I term natural genera, Desmobrya therefore 
includes part of the Ctenopteris and the whole of the Fhegopterh groups of Polypodium ; ali^o Gymno- 
gramma^ Goniapteris, Menisciiivt, and other genera of Polypodiece ; the whole of Pteridiere^ Asplenie^^ and, 
with a few exceptions, Ad^ostichie^j Aspidie^, Dicksonie<£^ and Cyatke^, 
I have here stated the obvious characters observed on examining examples of the two modes of deve- 
lopment; the differences become more evident on examining their internal structure. I cannot enter into 
details in this phice, the present collection not affording sufficient materials, nor the work space, to enable 
