As is the case with many other species included in the 
subtribe Ponereae, the segregates in Isochilus are on the 
whole more readily distinguished from one another on 
vegetative rather than on floral characters. The flowers 
of the various segregates have no constant characters 
whereby they may be easily distinguished. They may 
consist of a graduated series from large to small, and the 
freedom or adnation of the sepals may vary considerably 
even among flowers in the same raceme. 
According to J. A.Steyermark, plants of Jsochi/us are 
used in Guatemala in the treatment of colic, dysentery 
and other intestinal disorders. The species are commonly 
knownas ‘‘Calaqual’’, ‘‘Sanguinaria’’, ‘‘Nido de Pajaro”’ 
and ‘‘Cresta de Gallo”’. 
The key has been arranged so as to show the relation- 
ships of the various segregates. Extremes which repre- 
sent the typical entities retained are easily eliminated 
through the use of the key. However, it must be ad- 
mitted that intergrades are found between those forms 
connected by arrows in the key. 
In order to make this paper more complete, all of the 
species erroneously assigned to the genus JIsochilus have 
been included at the end of the paper where their present 
status is indicated. 
Isochilus R. Brown in Aiton Hort. Kew. ed. 2, 5 
(1813) 209. 
Leptothrium Kunth in Humboldt, Bonpland and 
Kunth Nov. Gen. & Sp. 1 (1816) 840, non Kunth 
Rév. Gram. (18380) 156. 
Isochilos Sprengel Syst. Veg. 3 (1826) 784, in part. 
Caespitose or repent epiphytic, terrestrial or rock- 
inhabiting plants with slender stems and numerous dis- 
tichous leaves, the rhizomes concealed by dark brown 
warty sheaths. Leaves strictly erect to spreading, linear, 
[2] 
