ME. a. BENTHAM OK OECHIDEJE. 325 



appears to comprise at least four distinct types of structure, 

 represented by the original O. coccineum, Salisb., by O. giganteum, 

 Lindl., O. suave, Lindl., and O. densum, lleichb. f., respectively. 

 The genus Siagonanthus and the two species ScapJiy glottis 

 parviflora and S. pendula of Poeppig and Endlicher (Nov. Gen. 

 et Sp. t. G7, 97, 98) would all three enter into the group of 

 O. suave. 



Subtribe 6. OnrciDiE^. — The Oncidiea? comprise a large pro- 

 portion of the pseudobulbous epiphytes familiar to our Orchid 

 growers, aud copiously illustrated in our horticultural publica- 

 tions. The genera are ail American, and have a characteristic 

 vegetation. The short rhizome bears stems, terminating usually 

 in a pseudobulb, crowned by one or, rarely, two leaves, and under 

 the pseudobulb are a few distichous leaves or leaf-sheaths, in the 

 axils o£ which are the leafless peduncles or scapes ; the fleshy 

 pseudobulbs apparently formed by the consolidation of the upper- 

 most leaf-sheath with the enclosed terminal bud. Sometimes the 

 pseudobulbs are almost sessile on the rhizome, and the scapes 

 arise also from the rhizome close to their base ; and in a few 

 genera the terminal pseudobulb is wanting, or only very tardily 

 thickened out, and the leaves are either distichously imbricate on 

 the short stem, or form with the peduncles an apparently radical 

 cluster. The leaves are fleshy, coriaceous, or, rarely, mem- 

 branous, neither plicate nor prominently many-ribbed. The 

 column is not produced at the base, forming no real nientum to 

 the perianth ; but in a few genera the labellum or the lateral 

 sepals, or both, are produced at their base into a spur. The pol- 

 linarium is usually well developed with a distinct stipes. The 

 thirty-five genera we have admitted into the subtribe may be dis- 

 tributed into five series, distinguished chiefly by the form of the 

 perianth. 



Series 1. Perianthium ealcaratum. — This includes six genera. 

 In four of them the spur of the labellum, often double, is en- 

 closed within a single spur, formed by the union of the base of 

 the two lateral sepals. Cryptocentrum is a new genus I have 

 proposed for an Ecuador plant of Jameson's, in which the very 

 long slender spur of the small flower in closely appressed to the 

 ovary, and enclosed with it in the sheathing bract. Biadeniam 

 Pcepp. and Endl. {Chcenanthe, Lindl.), two species, aud Compa- 

 rettia, Pcepp. aud Endl., two or three species, have the spur 

 slender, but diverging from the ovary. The flowers in Diadcnium 



