because each of these lines, although still sharing detecta- 
ble characters, displays an unequal rate of differentiation. 
These functional circles, or the number of functional an- 
thers present in these circles, are still employed today to 
characterize the two major subdivisions of the family. 
In Neuwiedia (Pl. VIII, fig. 2), there are three fertile 
anthers, one dorsal and two ventral. This is the only 
genus in the family Orchidaceae where fertile anthers are 
present simultaneously in both staminal circles. In this 
respect Neuwiedia, one of the three genera of the A pos- 
tastoideae, is perhaps the most primitive orchid: the other 
two genera, Apostasia and Adactylus are merely modifi- 
cations of the Neuwiedia-pattern. In Apostasia (PI. 
VIII, fig. 3), we observe a transformation of the dorsal 
anther into a staminode, while in Adactylus a further 
suppression completely eliminates this structure. 4 pos- 
tasioideae are set apart from the rest of the orchids by an 
additional series of correlated characteristics which will 
be discussed in further paragraphs. 
Although the floral diagram of A postasia is identical 
with Selenipedium (Pl. VIL, fig. 3) of the group Cypri- 
pedioideae, this identity is restricted to diagrammatical 
representation. The vegetative appearance, as well as the 
floral morphology in both of these groups, is very dis- 
similar. In A postasioideae, the filaments of the anthers 
are usually still present and recognizable; while in Cyp7i- 
pedioideae these structures are completely fused with the 
style. Furthermore, in Cypripedioideae, the shape of the 
staminode and the median petal exhibit a major devia- 
tion from A postasioideae, to such an extent that these 
two groups can hardly be interpreted as representing 
two subsequent stages of one evolutionary trend. 
The discontinuity between Meuwiedia and the monan- 
drous orchids is even greater. The floral diagram (PI. 
VILI, fig. 4) brings into focus a single criterion only: the 
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