324 
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THE GENERA AND SPECIES OF CULTIVATED FERNS. 
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petiolate ; pinnules flat, lunate, round at the apex, imbricate, lower ones flabellate, truncate at the base, and 
parallel with the rachis ; lateral, adherent to a short creeping rhizome. This beautiful Fern was introduced to 
Kew in 1845. 
Sect. II. — Davalliese, J. Smith. 
LEUCOSTEGIA, Presl (Davallia;, sp. of Authors).— -Name derived from leukos, white, and siege, a covering; 
alluding to the pale-coloured indusium. 
Sori round, terminal, often solitary on each segment, and seated in the sinus. Indusium orbicular or oblong, 
attached only by its base, the sides free. Veins forked ; venules direct, free. Fronds 
flabellate-multipartite, or tripinnatifid, with narrow linear-lanceolate or obtuse 
segments, usually trifid at their apices. Spore-cases vertical. — The leading charac- 
teristics of the genera of this section of Dicksonieae consist in the presence of 
a special indusium, forming, with the concave indusiform margin, an urceolate, 
bilabiate, or tubular vertical cyst, and in the spore- cases springing from a simple 
terminal receptacle. But in the present genus the indusium is of a very different 
description, being roundish or oblong, attached only by its base, and situated at 
some distance from the margin of the frond, which is quite flat. The genus 
thus forms a transition to Nephrolepis, in the tribe Aspidiese, with which it is 
somewhat analogous by the position of its sori and indusium ; but in habit it coin- 
cides with Davallia. Although eight or ten species of Leucostegia are described, 
only one of them is at present in cultivation. It is very distinct from the other 
portion of the Dicksoniea;, and is easily known by its scale-like indusium. Fig. 70 
represents a pinna of L. immersa (nat. size), with an indusium (magn.). 
1. L. immersa, Presl : Wallich. — A slender and very graceful deciduous stove 
species, from the East Indies. Fronds glabrous, deltoid, one to one and a half foot 
long, light green, bi-tri-pinnate ; pinna? triangularly elongate, especially below, 
their apices caudate ; pinnules oblong, membranous, deeply pinnatifid, with rather 
ovate segments, bluntly dentate, or bifid on the apex. Fronds lateral, articu- 
lated on a creeping rhizome. This species was imported about two years since by 
Messrs. Eollisson of Tooting, and has been lately introduced to Kew from Assam. 
JfWICROLEPIA, Presl. — Name derived from mikros, small, and lepis, a scale; 
XUit alluding to the indusium. 
Sori round or oblong, vertical, superficial, intramarginal ; receptacle elevated. 
Spore-cases spreading, rarely immersed in a cystiform cavity. Special indusium 
attached by its base and sides, widening outwards, with the free margin rounded or 
truncate. A r eins forked or pinnate ; venules direct, free. Fronds pinnate or bipin- 
nately multifid, one to four feet high, glabrous or villose. — 
The distinguishing character of this genus is in the structure 
of its indusium ; and it forms the connecting link between 
Leucostegia and Davallia. From the former it is distin- 
guished by having the indusium attached by its base and 
sides, and, from the latter, by not being tubulose. About 
twenty species are described ; but only one of them is at pre- 
sent in cultivation. Fig. 71 represents a pinnule of M. poly- 
podhides (med. size), and a sorus (magn.). 
1. M. polypodioides, Presl (Davallia, Bon; Dicksonia, tig. 70. 
Sicartz ; Polypodium speluncae, Zimiicus).- — An ornamental evergreen stove Fern, very 
extensively distributed throughout the tropics of the Eastern hemisphere ; the plant in 
cultivation is from Ceylon. Fronds triangularly-elongate, very hairy, three to four feet 
long, tripinnate, grass green; pinnules oblong acuminate, segments rather membranous, 
roundish ovate, pinnatifid, decurrent at the base, largest next the rachis, bifid or obtusely 
crenate on the margin. Fronds lateral, adherent to a creeping rhizome. We are indebted 
to G. Norman, Esq., of Hull, for cultivated specimens of this Fem ; it had been received 
from the continent. 
A.VALLIA, Smith. — Name commemorative of Edmund Davall, a Swiss botanist. 
Sori vertically oblong, intramarginal ; spore-cases pedicellate, attached to the apex 
of a venule, and exserted beyond the free margin of the indusium, which is usually 
inflated, forming with the concave indusiform margin a vertical bilabiate or tubular cyst, 
with the apex usually constricted. Veins forked, venules direct, free. Fronds of two kinds, sterile and fertile, 
with the fertile usually contracted, glabrous, or aculeate, from one to four or five feet high, varying from pinnate 
to decompound, the segments often unisorous. Rhizome frutescent, decumbent, scandent, fasciculate, or creeping. — 
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