the Dimerandra complex came to be called Dimerandra emargi- 

 nata, since the oldest basionym, published in 1818, was Onci- 

 dium emarginatum. 



As was stated above, the plants of Dimerandra look quite 

 different from the genus Epidendrum from which they were 

 segregated. Vegetatively they are similar in appearance to another 

 small group of plants originally described by Lindley as a dis- 

 tinct genus under the name of Gastropodium. Both groups have 

 the more or less thickened stems which, especially in dried con- 

 dition, become prominently sulcate or furrowed longitudinally. 

 The flower structure of these two groups is, however, quite dif- 

 ferent. Ames, Schweinfurth and Hubbard in their monographic 

 study of the genus Epidendrum in Central America placed Epi- 

 dendrum stenopetalum together with those species which now 

 comprise the genus Barkeria. Such a choice obviously served 

 some practical solution in preparing a key for identification 

 rather than expressing actual relationships. Attention must be 

 called to one of the remarkable aspects of Dimerandra flowers, 

 the random lobation occuring in the petals and the lip. This 

 must be emphasized because I have seen lips of individual flow- 

 ers where lobation may occur so symmetrically that the actual 

 blade appears to be three-lobed, yet such a character may not be 

 present on the second flower of the same plant. 



Members of the genus occupy a considerable area of the 

 American tropics, ranging from Mexico through Central Amer- 

 ica to northern and western South America, including the Ori- 

 noco and Amazonian basins. They are conspicuously absent from 

 the West Indian Islands. Two species, D. elegans and D. emar- 

 ginata, have the widest distribution; their pattern of variability 

 in both vegetative and floral structures appear to be directly 

 proportional to the geographic area they inhabit. The remaining 

 species are rather restricted either in area or in frequency or 

 both. Dimerandra emarginata, although described originally 

 from Guayana, is most common in Central America, from Mex- 

 ico to Chiriqui, in Panama. One of the most interesting charac- 

 ter separations in the shape of the petals occurs on both sides of 

 the isthmus of Panama. Plants with lanceolate-elliptic petals 



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