deeply cordate at apex, much surpassing the rostellum, during 
anthesis becomes flattened and arcuately curved backwards: pol- 
linia clavate with an ovate to roundish viscidium. Ovary obli- 
quely fusiform, sessile. 
Terrestrial plants with fasciculate, fleshy, tuberous roots. 
Leaves, when present, basal, petiolate, rosulate. Scape erect, 
slender, remotely several-vaginate which decrease in size up- 
wards, terminated by a more or less densely many-flowered, 
commonly secund spike. Flowers small to minute in size. 
LECTOTYPE: Spiranthes Galeottiana A. Rich. [Britton & 
Wilson, Sci., Surv. Porto Rico 5(2): 186, 
1924] 
Eight species native to the American tropics and subtropics. 
Index to species 
Mesadenus affinis (C. Schweinf.) Garay, comb. nov. 
Basionym: Spiranthes affinis C. Schweinf. in Bot. Mus. Leaf. 4: 101. 1937. 
Mesadenus Chiangii (Johnst.) Garay, comb. nov. 
Basionym: Spiranthes Chiangii Johnst. in Phytologia 45: 449, 1980. 
Galeottianus Schltr. = Mesadenus polyanthus (Rchb.f.) Schltr. 
Glaziovii (Cogn.) Schltr. 
lucayanus (Britt.) Schltr. 
minutiflorus (Rich. & Gal.) Schltr. = Microthelys minutiflora (Rich, & 
Gal.) Garay 
polyanthus (Rchb.f.) Schltr. 
Mesadenus rhombiglossus (Pabst) Garay, comb. nov. 
Basionym: Hapalorchis rhombiglossus Pabst in Bradea |: 468. 1975. 
Mesadenus Stahlii (Cogn. ) Garay, comb. nov. 
Basionym: Spiranthes Stahlii Cogn. in Urb. Symb. Antill. 6: 341. 1910. 
Mesadenus tenuissimus (1..0.Wms.) Garay, comb. nov. 
Basionym: Spiranthes tenuissima L.O.Wms. in Bot. Mus. Leafl. 
12:235, 1946. 
Microthelys Garay, gen. nov. 
Etymology: Micros =smalland the/ys = female. describing 
the nature of the rostellum. 
Sepala subsimilia, parallela, apicibus leviter divergentibus;: 
sepalo postico concavo, columnae dorsaliter adnato: sepalis 
lateralibus obliquis, mentum non formantibus. Petala sepalo 
postico agglutinata, basi oblique decurrentia. Labellum late bre- 
336 
