LANKESTERIANA


characters sufficiently distinct to warrant generic
recognition, among which the presence of tubular
sheaths concealing the ramicaul, often bearing
digitate trichomes, a leaf abscission layer without
the "node" which may be found in racemose
species of Pleurothallis, the fascicled
inflorescence, and the often thickened apices of the
petals, sometimes developed into osmophores
(Luer 1982). The original circumscription of
Myoxanthus was emended by Luer (1992) in his
systematic monograph of the genus, with the
description of subgenus Silenia to include the P.
aspasicensis complex, encompassing 3 species with
a fascicle of single, successive flowers borne
terminally from the ramicaul, fleshy flowers exter-
nally short- pubescent, and ciliate anther cap.
Eventually in 1995 Luer proposed to include
Myoxanthus subgenera Satyria and Silenia in
Pleurothallis subgenus Acianthera in order to
restore a circumscription of Myoxanthus sensu
strict (Luer 1995).
 The generic delimitation of Myoxanthus among
other pleurothalloids is supported by a unique
assemblage of morphological characteristics and
anatomical features revised by Pridgeon and Stern
(1982). The presence of two series of foliar veins
and a medullated stele in the root is characteristic
of Myoxanthus and may be found elsewhere in the
Pleurothallidinae only in Octomeria and in the
Pleurothallis aspasicensis complex. Spiral thicken-
ings in hypodermal cells and mesophyll idioblasts,
which are present in most pleurothallids, are
notably absent from all the tissues of Myoxanthus
and the P. aspasicensis complex (Pridgeon & Stem
1982).
 In view of the diagnostic anatomical characters
which allow recognition of evolutionary affinities
in the Pleurothallidinae and to preserve the natural-
ness of Myoxanthus, we prefer to maintain the P.
aspasicensis complex as Myoxanthus subgenus
Silenia and we therefore propose the following
Myoxanthus species new to science:

Myoxanthus vittatus Pupulin & M.A. Blanco, sp.
nov. FIG. 1

 TYPE: COSTA RICA. San Jose: Perez Zeled6n, El
Brujo, near Rio Division, 450 m, 30 Jan. 2000,


flowered in cultivation at Jardin Botanico
Lankester, 3 June 2001, M.A. Blanco 1324 (holo-
type, USJ!; isotype, SEL!).
 Species Myoxantho aspasicensi (Rchb.f.) Luer
similis, sed plant floribusque omnine minoribus,
ovario pubescente, sepalis purpureo vittatis, interne
laevis, synsepalo lanceolato, apice petalorum
dorsaliter tuberculato, labello ligulato apice laevi
differt.

 Plant epiphytic, cespitose, up to 17 cm tall, roots
coarse. Ramicauls stout, erect, 4-7 cm long,
enclosed by 3-4 loose, tubular sheaths sometimes
fragmented. Leaf erect, thickly coriaceous, narrow-
ly lanceolate-elliptic, minutely emarginate, 7-10 cm
long, 1.3-1.5 cm wide, cuneate below into a condu-
plicate, sessile base. Inflorescence a fascicle of sin-
gle, successive flowers, at the apex of ramicaul,
the peduncle sparsely pubescent, 8-13 mm long,
subtended by a papyraceous spathe 1.4-1.6 cm
long; pedicels 2-3 mm long; ovary less than 1 mm
long, densely pubescent. Flowers small, whitish,
longitudinally striped with purple, fleshy, densely
short-pubescent externally, glabrous within. Dorsal
sepal linear-oblanceolate, obtuse, 10-12 mm long,
3 mm wide, 5-veined. Lateral sepals connate into a
lanceolate, shortly emarginate, concave synsepal,
10-13 mm long, 4-5 mm wide, each half 4-veined.
Petals fleshy, linear-oblong, obtuse, minutely apic-
ulate, adaxially provided with a tuft of short papil-
lae near the apex, 4 mm long, 1 mm wide, 3-
veined. Lip 3-lobed, ligulate, subacute, 4 mm long,
2.5 mm wide between lateral lobes; the apical lobe
smooth, slightly undulate along the margins; the
lateral lobes erect, narrowly uncinate, antrorse; the
disc with an erect, narrow, low, channeled callus
above the base, extending in front into a low keel
just to near the lip apex, laterally provided with a
pair of low lamellae extending to the apex, hinged
on the end. Column arcuate, semiterete, 1.6 mm
long, provided with narrow wings above the mid-
dle, the foot less than 1 mm long. Anther cap glo-
bose, with long hairs on the upper margin, 2-celled.
Pollinia 2, obovoid, flattened, on a short caudicle.
ETYMOLOGY: from the Latin vittatus, "longitu-
dinally striped", in reference to the stripes on sepals
and petals.