The relationships of meiracyllium (Orchidaceae)

Only two species are known of the Mexican and Central American genus Meiracyllium, both described by H. G. Reichenbach, Jr. They are small creeping epiphytes with short unifoliate secondary stems that are scarcely thickened, but bear very fleshy oblong or elliptic-oblong leaves. Though small, the flowers are conspicuous by their bright rose-purple color, as well as by a pleasant spicy fragrance. Schlechter, in his "System der Orchidaceen," placed this genus in the subtribe "Laelieae" ( Epidendrinae), near Sophronitis, and subsequent writers have followed this course. Meiracyllitun differs, however, from all other genera of this group in the structure of the column and pollinia. In other genera of the "Laelieae" the anther is terminal or (in Epidendrum) somewhat dorsal, and is separated from the stigma by a short partition-like rostellum, whereas in Meiracyllium the anther is distinctly dorsal and the rostellum forms an erect tongue-like projection which is a quarter to a third the length of the column. In the "Laelieae," as delimited by Schlechter, the pollinia are almost invariably laterally flattened, and bear distinct straplike ventral caudieles; a viscidium or gland' is present at least in true Epidendrum and in Sophronitis, but is semi-liquid or poorly defined. The pollinia of Meiracyllium are narrowly clavate and taper to an indistinct terminal caudiele, by which they are attached to a shiny black or dark brown viscidium at the apex of the rostellum. Since the structure of the column and pollinia are assigned such great importance in orchid classification, it seems strange that the structure of Meiracyllium has been so consistently overlooked. Porsch, in describing Meiracyllium wettsteinii from Brazil, discussed the relationships of this genus and considered it to be closely allied to Sophronitis. Porsch's plant, however, was Neolautchea pulchella Kriinzlin, a close ally of Sophronitis violacea Lindl. True Meiracyllium differs from Sophronitis quite strongly in all but size of plant and number of pollinia (which differ in structure). The column of Meiracyllium is immediately reminiscent of the Asiatic genus Podochilus and its allies. The Asiatic plants, however, are markedly different in habit, having elongate stems with many distichous leaves; the flower structure is also somewhat different, especially in the more complex lip. The relationship between Meiracyllium and Podochilus does not appear to be especially close. Bentham and Hooker, in the Genera Plantarum, assigned Meiracyllium to the subtribe Pleurothallidinae with a query; examination of living plants indicates that there is probably a relatively close relationship here. The habit of Meiracyllium is closely matched by that of many of the Pleurothallidinae. The number and structure of the pollinia is similar to that of Octomeria and Yolanda. The structure of the column is very closely duplicated by some species of Lepanthes (e.g., L. woodiana Fawcett & Rendle) which, however, have only two pollinia. Clavate pollinia are the rule among the Pleutrothallidinae, and a distinct viscidium terminal on the rostellum is frequent. The rostellum is generally much less conspicuous than in Meiracyllium, but it is tongue-like and