342 MR. HENRY RIDLEY ON ORCHIDEZ AND 
Though the position of the flowers is quite unlike that of the 
other species, yet as the plant sufficiently resembles in habit 
the others, and the flower has just the same structure, it cannot 
be referred to any other genus. Of all the species it is nearest 
to B. alticola, Ridl. 
LEUCOLENA, Ridl. 
L. oxnata, Ridl. iz Journ. Linn. Soc. (Bot.), xxviii. (1891) 
p. 340, t. 43. 
Hab. Malacca: Bukit Sadanen ! 
POLYSTACHYA, Hook. 
Polystachya is one of the very few epiphytic genera of orchids 
which are common to both hemispheres. The headquarters of 
the genus appears to be Africa. There are but few species in 
the East Indies; but there are a number in the New World. 
The Malayan species are not only few in number but always 
scanty in individuals, so that it is not easy to get a good series 
of specimens for comparison. Three species are mentioned in the 
‘Flora of British India’; two of these, P. Wightti, Reichb. f., 
and P. purpurea, Wieht, belong to the simple-racemed series, 
and are apparently closely allied to P. luteola, Hook. To these 
I have added P. singapurensis and P. siamensis. The latter 
much resembles P. luteola, Hook., if I am correct in referring to 
that species a plant I formerly collected in Pernambuco; and 
it even more resembles a specimen received from Dublin 
Gardens, having been imported from Trinidad. It is quite 
possible that all these species, together with some others from 
the African region, will eventually be reduced to a single one. 
The chief differences lie in the form and proportions of the lip. 
P. penangensis, sp. nov., belongs to the P. zeylanica group 
with a longer branched panicle. The development of the 
panicle is not a good sectional character, as there are inter- 
mediate forms between the simple raceme and panicled 
inflorescence in the African region. I am very doubtful as to 
the affinities of the genus, but as the pollinia usually at least 
possess an oblong pedicel, it is perhaps best to retain it in the 
neighbourhood of Cymbidieew. All are probably self-fertilized, 
as some species undoubtedly are, and this makes the form of 
the pollen masses and their pedicel often difficult to make out, 
for fertilization has begun before the flower opens. 
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