» 
MR. R. ALLEN ROLFE ON THE GENUS VANILLA. 443 
AFFINITIES. 
Vanilla belongs to the small subtribe Vanzllee, which com- 
prises also Hpistephium, Eriazis, Galeola, Sobralia, and Sertifera, 
though the latter two are excluded by Pfitzer. The species of 
Epistephium are erect herbs, natives of tropical America, with 
purple flowers and a calyculus at the base of the perianth 
segments—an organ which is also found in Vanilla palmarum. 
The species of Galeola are leafless saprophytes, in colour ranging 
from yellow to brown and red; the genus ranges from India 
and Japan to Australia. riazis is from New Caledonia and 
has been referred to the latter, but has leafy shoots besides some 
differences in structure. Sobralia and Sertifera are erect 
herbs, natives of tropical America, and quite distinct in habit. 
CLASSIFICATION. 
In the following enumeration an attempt has been made to 
arrange the species in as natural a sequence as possible, so far 
as the materials at hand permitted, but some modification is 
sure to be found necessary when flowers and fruit of all the 
species are known. Owing to the incomplete materials of some 
of the species, I have had to utilise geographical limitations in 
a few cases in the key, but in all such cases the species 
bracketed together appear to be intimately allied. The 
division into leaf-bearing or leafless species seems to be the 
most natural, and the latter evidently forming a very highly 
specialized group are placed at the end. Conversely, those with 
the tube extremely short and the lip without a central crest are 
placed at the beginning, being obviously the least specialized. 
The remainder form @ fairly natural transition between the 
two. 
GEOGRAPHICAL DISTRIBUTION. 
The genus is widely diffused throughout the forest region of 
the tropics, but the species themselves are very local. From 
the annexed table it will be seen that of the 50 species, 29 are 
American, 1] Asiatic, and 10 African, the headquarters of the 
genus being in Brazil and Guiana, where 15 species occur, but 
of these only four are common to both, so far as our present 
knowledge extends. 
