328 THE ORCHID REVIEW. 
become ancestral ones if sufficiently beneficial to give rise to a dominant 
group of organisms, the acquired characters being then handed down to all 
the descendants in common. But when a group becomes dominant, and 
widely diffused, some of its members again come under new conditions of 
environment, still newer adaptations arise as the group diverges, and the 
original adaptive character having served its purpose, may now only persist 
in a modified or rudimentary form throughout the new group. From 
these remarks the significance of the two sets of characters will be 
apparent. 
In the following sketch I have aimed at a natural arrangement, as far 
as the broad features are concerned, but it is quite possible that future 
discoveries may render modification necessary in some details. 
SUBORDER I. DianpR&. 
This suborder is characterised by the presence of either two or three 
perfect stamens situated on one side of the flower, and by the pollen grains 
being invariably simple. The stamens represent the lateral pair of the 
inner staminal whorl, and the median one of the outer whorl. It contains 
about a hundred known species, now arranged in seven genera. It is 
sparingly diffused through the northern hemisphere, the tropics of America 
and Asia, and along the Malay Archipelago to tropical Australia, but has 
not been detected in any part of Africa. 
Trise I. Apostasiea. 
Perianth regular, or nearly so, with subequal segments; column very 
short, filaments slender, anthers more or less elongated, pollen dry; style 
slender with minute stigma. The tribe contains three genera and over a 
dozen species, and ranges from Continental India and Ceylon through the 
Malay Archipelago to tropical Australia. 
Key to the Genera. 
Three stamens all perfect, linear or oblong ; flowers in dense erect spikes 
1. NEuwrepia, Blume. 
Dorsal stamen imperfect or absent; flowers in pendulous simple or branched 
spikes. 
Dorsal stamen modified into a linear staminode, partly adnate to the 
style; anthers with oblique base 2. AposTasiA, Blume. 
Dorsal stamen entirely suppressed; anthers with equal base 
3. ApactyLus, Rolfe. 
I. NEUWIEDIA. 
The most ancestral of existing Orchids, and of remarkably simple 
structure, as the linear versatile anthers with slender filaments, and the 
distinct style, are very different from those of most Orchids, though it agrees 
in every other Tespect. It ranges from Malacca and Penang to New Guinea, 
six species being known. 
