Me 
LS Hf if 
uM 
‘ LY 
A B 
Fig. 5. Drawings from wire-plasticine models to illustrate the nature 
of the vascular supply to the labellum and spur. 
A. When the spur is single; B. When the spur is double. 
main traces underlying the sepals. "Then, in some genera, 
each of the main traces underlying the lateral petals 
(LP) gives off a trace (al and a2) into the gynostemium, 
these representing the lateral stamens of the inner whorl. 
In some other genera, the main traces of the lateral sepals 
(LS) each give out a trace (A2 and A3) into the gyno- 
stemium; these represent the traces belonging to the lat- 
eral stamens of the outer whorl. The commoner condition 
is the presence of the traces representing the lateral sta- 
mens of the inner whorl. In some genera (Dendrobium, 
[ 74 ] 
