Tlio indusium is white, semi-transparent and entire. The plant is
one of unusual elegance, both on account of its minute subdivision,
and its smooth shining surface.
No one who has obsorvod the venation in this plant, and is
acquainted with our British Asplenieæ, can fail to notice the similarity
in form aud division and in the condition of tho veins, that
exists between some of its ultimate pinnules, especially the shorter
and broader ones of the less divided fronds, and some of tho fronds
of Asplenium septentrionale ; there is no definite midvein in either,
but a series of fm’cations only. This plant alone furnishes sufficient
evidence against tho adoption of the Amesium or Acropteris group as
a gonus.
This acute variety differs from the normal foi-m of Adiantum-
nigrum iu its more subdivided fronds, in which tho deltoid form is
usually strongly developed, in its thinner, harsher, and more papery
texture, and in the presence throughout of linear acute erect segments
and teeth. As to its distinctness, our enumeration of the varieties or
forms occm-ring in Great Britain -will show that in composition it is
simulated by dcoompositum ; in texture by oxypliyllum especially, and
by intermedium in a considerable degree ; and in the presence of linear
segments or teeth, both by oxypliyllum; in which the teeth though
sharp are short, and by fissum and acutidentatum, in which the narrow
marginal divisions are, perhaps, rather monstrous developments
of the teeth, than normally narrow divisions of the pinnules. These
points of resemblance, however, and the occurrence of other foreign
intermediate states, have determined us in retaining acutum as a
variety of Asplenium Adiantum-nigrum. We have only seen true
examples of this variety from Ireland, in which the following habitats
are recorded :—Kerry ; Turk Waterfall, KiUarney, Br. Mackay,
Dr: Allchin, and others ; foot of Oromaglaun near the lower end of
the upper lake, Q. Maw ; above Blackstones, Glouin Caragh, Inve-
ragh, G. Maw ; Cahir Conree, a mountain near Tralee, W. Andrews.
Dublin; Dublin mountains, 1854, D. Orr. Cork: near Garry-
cloyne. Blarney, 1857, Miss Townsend. Mr. C. Johnson, in
Sowerby’s Ferns of Great Britain, states that in 1821, he gathered
a plant undistinguishable from this, on the walls of the Cathedral
of St. Asaph in Wales ; it has further been reported from
Jersey on the authority of M. Piquet ; and a specimen from Combe
Boyal, South Devon, sent by Miss Iloseason, approaches it very
nearly. Sherard’s plant from the Mourne Mountains in Down,^ the
A s p l e n i u m Adiantum-nigrum, ¡3. of Sir J. E. Smith, and identified
with acutum by Mr. Newman, is not referrible here, but to Athyrium
Filix-foemina (see p. 37). Mr. Maw mentions that it prefers the drier
parts of moist woods, occurring in situations where the tree-growth
is not very dense. [Plate LXXII.]
2. obtusatum (M.). This may bo considered as a less developed
though matured condition of the species, than that which we have
regarded as typical. It is a comparatively smaU and dwarf plant,
and assumes an ovate-acuminate rather than a triangular outline ;
some specimens are not more than two inches high, and others very
marked in character are six or eight inches high. The smaller
specimens are scarcely bipinnate ; the pinnæ are short and bluntly
triangular ; the pinnules are roundish-obovate, and very mdistmotly
toothed. The larger examples are tripinnate, with their primary
and secondary pinnules corresponding with the pinnæ and pinnules
of the smaU specimens. It is probably not uncommon, specimens
from the three kingdoms being before us. This form is less defined
than some others, the smaUer states of the common form occasionally
approaching it very closely, hut as it occurs under different phares,
it seems to claim recognition, at least as a variety of secondary importance.
Thus, though often scarcoly bipinnate, we have received
from Mr. D. Moore specimens from Antrim, Ireland, which though
tripinnate are clearly referrible here. The other specimens we have
seen are from ;-K en t : Sandgate, 8. 0. Gray. Devon: Torquay,
Miss F. Burmester. Yorkshire: Wensleydale, C. H. Compton.
Stirlingshire: near Stirling, Mrs. Macleod. Argyleshire; Ardrishiag,
T. M. Ireland : Newtown Castle, Br. Allchin; Fojmes, Mrs. Barrington;
foot of Slieve More, Dugort, Isle of AohiH, B. Barrington.
Guernsey, G. Wolsey. [Plate LXXI A.]
3. leptorachis (M.). This is a small-fronded elegant form remarkable
for the length of its stipes and the small size of the parts of its
frond. The stipes is about seven inches long, slender ; the raohis
also is slender ; the leafy portion or lamina is about throe inches
long, ovate, shortly acuminate, tripinnate ; tho pinnæ alternate, the
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