ORCHIDACE^ 



not restricted to the species of the eastern tropics, as Erythrodes 

 secunda Ames, a native of Mexico, has a bilobed sac in the flowers 

 I have examined, and proves that this character is not, as Schlech- 

 ter would have us beheve, geographically limited in the group 

 under consideration. The slightest tendency toward a lobing of 

 the sac demands an arbitrarily fixed hmit to guide us as to the 

 point where Physums should end and Erythrodes should begin. 



In my studies of numerous specimens of Erythrodes from the 

 tropics of both hemispheres, I have endeavored to find characters 

 correlated with a conspicuously bilobed sac that would make 

 cleavage possible along geographical lines and point the way to 

 an absolute separation of the palaeotropical from the neotropi- 

 cal species. The gynostemium, however, in which one would ex- 

 pect to find the more conservative structures of the flower, is 

 very similar in all the species examined and exhibits only those 

 variations, such as differences in the length of the anther or ros- 

 tellar processes, that would naturally be expected and that occur 

 in different species irrespective of their origin. Schlechter con- 

 cluded that the gynostemium is more slender in the Old World 

 species than in those of the New World, but I have been unable 

 to demonstrate that this difference exists. 



It is noteworthy that the carinae, complanate or papilliforni 

 calli that occur on the anterior wall of the sac in many species 

 of Erythrodes have received very little attention ; in fact they 

 have been overlooked or disregarded by systematists who have 

 characterized the genus. Bentham and Hooker failed to mention 

 them in the Genera Plantarum and in his work on the orchids for 

 Engler and Prantl's Das Pflanzenfamilien Pfitzer used the ab- 

 sence of warts from the interior of the sac as a key character to 

 distinguish this genus from Queteletia. The neglect of these 



structures is altogether surprising because their position on the 



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