TROPICAL AMERICAN ORCHIDS 
wide, shortly unguiculate, oblong, rounded at the tip, 
3-nerved, with the nerves prominent beneath, margin 
sparsely serrate-dentate, upper surface densely and minutely 
glandulose especially along the middle of the disc, with the 
glands near the centre in well-defined transverse rows. Disc 
lightly bicarinate, with the keels intramarginal and shortly 
denticulate. Column hardly 4 mm. long, produced at base 
into a short foot, apex trilobulate, with the posterior lobule 
obscurely erose-denticulate. 
Pleurothallis periodica is closely allied to P. Brighamii 
S. Wats., from which it differs in the more glandulose den¬ 
ticulate labellum with shortly denticulate carinae and in the 
absence of an angular marginal projection on each side near 
the base. [Plate 4.\ 
Costa Rica, Peralta, C. H. Lankester 463, July 13, 1923. 
Flowers hyaline, yellowish, deeply tinged and striped with 
maroon purple. Labellum and petals very dark maroon. 
(Type in Herb. Ames No. 27021.) 
Pleurothallis pompalis Ames sp. nov. Radices 
libratae, albidae, glabrae. Rhizoma valde abbreviatum. 
Caules secundarii caespitosi, elongati, paucivaginati, mono- 
phylli. Vaginae nervosae, tubulatae. Folium oblanceo- 
latum, in petiolum sulcatum contractum, apice bilobulatum 
apiculo interjecto. Pedunculus gracilis, cum racemo folium 
multo superans. Racemus laxus, verisimiliter secundus, plus 
minusve decemflorus. Bracteae racemi infundibuliformes, 
acutae. Pedicellus cum ovario gracilis. Sepala lateralia 
paene usque ad apicem cohaerentia, laminam anguste 
lanceolatam purpureo-villosam formantia, atropurpurea. 
Sepalum dorsale lineari-lanceolatum, acutum, intus dense 
purpureo-villosum, extus per medium alte carinatum. Pe- 
tala late ovata, acuta, antice prope basim protuberantia. 
Labellum trilobatum, anguste unguiculatum; lobo medio 
oblongo, obtuso, margine deflexo; lobis lateralibus ab- 
breviatis, antice in lobulum attenuatum contractis. Col- 
umna usque ad apicem dilatata. 
Roots fibrous, whitish, smooth. Rhizome abbreviated. 
Secondary stems crowded, erect or ascending, 5-7 cm. long. 
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