As has been stated more than once, the vascular pat- 
tern is not always strictly fixed, but is somewhat plastic 
in this species. In all of the three instances of deviations 
to be described below, the origin and nature of the trace 
A1 is very consistent, as in the other monandrous orchids. 
It is the nature of the other vascular traces of the stam- 
inal whorls that present interesting variations. In the first 
deviation (Fig. 9 C and D) the staminal vascular traces 
arise from the point of trifurcation of the main traces, LS. 
Thus the traces A2 and A8 complete the outer whorl 
of stamens. In the second deviation (Fig. 9 EK and F), 
the main trace under one of the lateral sepals give rise 
to the trace A2 (representing a lateral stamen of the 
outer whorl), whereas on the opposite side the main trace 
lying under the lateral petal gives the trace a2 (repre- 
senting a lateral stamen of the inner whorl). In the third 
deviation (Fig. 9 G and H, left), there arises a com- 
pound staminal trace, al+A2, whereas on the opposite 
side the main trace under the lateral sepal gives rise to 
A8, representing a lateral stamen of the outer whorl). 
In addition to these two, the main trace, MP (lying under 
the labellum), also sends out a slender offshoot, a8, into 
the gynostemium; this trace is to be interpreted only as 
representing the median stamen of the inner whorl. ‘Thus, 
these deviations, when taken together, reveal the pres- 
ence of all of the six stamens belonging to the two whorls. 
This also makes it possible to visualize the fact that all 
of the six stamens were once functional in the ancestral 
orchid flower. 
In passing, it may also be noted by a study of these 
illustrations (Fig. 9) that the plasticity of vasculature is 
not confined to the staminal whorls alone but is extended 
to the labellum also, whereby the latter is supplied by 
supernumerary marginal traces in certain instances. 
Before proceeding to the general discussion, it 1s im- 
[ 81 | 
