portant to have an idea of the changes that are brought 
about in the vascular pattern of the flower during the 
development of the flower itself. This type of study was 
confined only to Dendrobium and Cymbidium, but I feel 
that the results obtained may in general be applicable to 
other orchids also. Here again, particular attention may 
be laid upon the development of ‘‘compound’’ staminal 
traces. 
In the young condition (when the microsporangium is 
just differentiated) the marginal traces of the adjacent 
lateral petal and sepal show the following features (Fig. 
10 A): The staminal traces al, a2, A2 and AB are all dis- 
tinct from one another, although their place of origin is 
shifted higher up to the point of concrescence of the ad- 
jacent marginal traces; but actual concrescence is not 
yet affected. During subsequent development, concres- 
cence and adnation proceed to such a degree that the 
distinct origin of the staminal traces becomes totally 
obliterated so that they are seen only as ‘‘compound’’ 
Al 
air Ar a2+A3 
is 
Fig. 10. Vascular diagrams of Dendrobium showing the juvenile con- 
dition in A and the adult condition in B. 
[ 83 | 
