DISSECTIONS.--1. Lip and column, seen sideways; 2. Front view of ditto: _magnified_. Plate 21 [Illustration: Odontoglossum Hallii.] PLATE XXI. ODONTOGLOSSUM HALLII. COLONEL HALL'S ODONTOGLOSSUM. O. (EUODONTOGLOSSUM, _Lindl._) pseudobulbis ovatis, ancipitibus 1-2-phyllis, foliis ensiformibus in basin angustatis, racemo multifloro (raro sub-paniculato), sepalis petalisque ovato-lanceolatis unguiculatis labello oblongo acuminato lacero, cristâ baseos lamellatâ multifidâ, columnæ alis dente superiore aristato. ODONTOGLOSSUM HALLII, _Lindl. in Bot. Reg. sub t._ 1992, _et Folia Orchid._; _Reichenbach fil._ Xenia, i. 63; _Walpers Annales_, vi. p. 828. Habitat in PERU (western declivity of Pichincha), _Hartweg_; Valley of LLOA, at elevation of 8000 ft., _Col. Hall_; N. GRENADA in forests of Pamplona, 8500 ft., _Linden_. DESCRIPTION. PSEUDOBULBS _ovate, 2 to 4 inches long, compressed, 2-edged, bearing generally one, occasionally two, lanceolate_ LEAVES, _a foot or more long_. RACEME _many (10-20) flowered, occasionally though rarely branched, 2 to 3 feet long_. SEPALS _and_ PETALS _nearly equal, ovate-lanceolate, exceedingly unguiculate, from an inch to (in some varieties) an inch and a half or even 2 inches long, yellow with large, often very dark, blotches of purplish-brown_. LIP _white, with a few rich spots, oblong-acuminate, jagged at the edges, with a large and handsome yellow_ CREST, _consisting of a multitude of flattened but sharp-pointed teeth, pointing sideways and downwards_. COLUMN _white, winged, the wings broken into teeth or cirrhi, of which the uppermost is much the largest_. This fine _Odontoglossum_ was one of the earliest known though one of the latest to reach us alive. It is now (1873) plentiful enough, and forms a most attractive object in our spring Orchid-shows. There are many varieties differing greatly in the size and marking of their flowers, but all maintaining the unguiculate sepals and petals which chiefly distinguish it from _O. luteo-purpureum_ (Pl. 17), to which it is indeed very nearly allied. _O. Hallii_ is abundant in New Grenada and Peru, but is seldom met with at a lower elevation than 8000 feet, hence it is quite at home in the coolest part of the "cool Orchid-house," in which it grows and flowers very freely indeed. In the woodcut, a solitary flower of a larger variety of the species is represented, natural size. [Illustration] Plate 22 [Illustration: Odontoglossum Roseum.] PLATE XXII. ODONTOGLOSSUM ROSEUM. ROSY ODONTOGLOSSUM. O. pseudobulbis ovatis ancipitibus 1-phyllis, foliis oblongo-lanceolatis racemo gracili multifloro duplo brevioribus, bracteis ovatis concavis subangulatis pedicellis duplo brevioribus, sepalis petalisque lanceolatis, labello trilobo basi bilamellato: lobis lateralibus nanis rotundatis intermedio obcuneato acuto, columnâ elongatâ apice alis 3 membranaceis integris auctâ.