As the first specimens of the _white_ variety of _O. Alexandræ_ were collected by Mr. Weir, it is only fitting that his name should be associated with it, just as the name of his rival Mr. Blunt has been connected with the variety distinguished by its crimson spots. Plants of both frequently acquire a reddish tint both in their bulbs and leaves, a tint which, wherever it occurs, is a sure criterion by which _O. Alexandræ_ may be distinguished from other Odontoglossa that closely resemble it in habit. _O. Alexandræ_ proves to be a slow grower, and to require the coolest compartment of the Peruvian house. If this condition be attended to, it gives no trouble whatever, and produces its exceedingly durable flowers very freely indeed. Dr. Triana met with it on the trunks of very large trees with dense foliage, ten leagues from Bogotá, and also at Pacho. DISSECTIONS.--1. Lip and column, seen in front; 2. Ditto, seen sideways: _magnified_. Plate XX [Illustration: Odontoglossum maculatum.] PLATE XX. ODONTOGLOSSUM MACULATUM. SPOTTED ODONTOGLOSSUM. O. (XANTHOGLOSSUM) pseudobulbis oblongis compressis monophyllis, foliis oblongis nervosis acutiusculis, racemis subpendulis multifloris brevioribus, bracteis navicularibus herbaceis ovario brevioribus, sepalis lineari-lanceolatis acuminatis discoloribus, petalis oblongis undulatis acuminatis, labello cordato acuminato subcrenato, appendice unguis bivalvi concavâ cochleari apice liberâ bidentatâ per medium argute serrulatâ, columnâ pubescente subapterâ. _Lindl._ ODONTOGLOSSUM MACULATUM, _Llave_, _Orch. Mex._ 2, 35; _Bot. Reg._ 1840, _t._ 30; _Pescatorea_, _t._ 28; _Lindl. Fol. Orch._ Habitat in MEXICO, _Lexarza_, _Barker_, _Karwinski_. DESCRIPTION. PSEUDOBULBS _narrow, oblong, much compressed, from 2 to 4 inches long, 1-leaved_. LEAVES _lanceolate-oblong, nervose, more or less sharp-pointed, shorter than the flower-scapes_. BRACTS _boat-shaped, acuminate, the lower ones shorter than the upper ones, nearly as long as the ovary_. RACEMES _nodding, sometimes pendulous, 5- to 12-flowered, about a foot long_. FLOWERS _variable in size and colour, which is sometimes a brightish at other times only a greenish-yellow, spotted with brown_. SEPALS _brown inside, linear-lanceolate, acuminate_. PETALS _rather wide, oblong, waved, acuminate_. LIP _heart-shaped, acuminate, slightly crenate, with a two-cleft process forming a pair of blunt teeth at the upper end of the claw_. COLUMN _pubescent, clavate, wingless_.