Material was fixed in formalin-acetic-alecohol, and serial 
microtome sections of the entire flower buds were pre- 
pared following the customary methods. Basic fuchsin 
or crystal violet, with a counter stain of light green, was 
employed for staining the vasculature and ground tissue 
respectively. This combination gave satisfactory contrast. 
In addition to sectioning, entire flower buds of some 
species were cleared first in chloral hydrate and subse- 
quently in lactic acid. This method was especially suit- 
able for small flowers (like Oberonia, Diplocentrum, ete. ) 
and those with delicate floral parts (like Zeuavine, Haben- 
aria, etc.). But for larger flower buds (Cymbidium, Hu- 
lophia, Dendrobium, ete.), a certain amount of trimming 
of the perianth was essential. 
After observing both serial sections and cleared ma- 
terial, wire-plasticine models were constructed, and the 
three dimensional drawings reproduced here have been 
sketched from such models. The vascular diagrams that 
accompany the text have been drawn as seen from above; 
however, the exact places of origin of certain traces have 
been slightly exaggerated and spread out in one plane 
in order to bring out the details. 
Structure of the Flower 
The orchid flower is bilaterally symmetrical. The ovary 
is inferior and bears at its upper extremity the other floral 
organs. There are two whorls in the perianth, each whorl 
consisting of three members. Often, all the members of 
the outer whorl are similar in appearance, though some- 
times the median member (often designated as the 
‘*hood’’ or the ‘‘dorsal sepal’’?) may be somewhat more 
conspicuous than the lateral members either in pattern 
or size. In the inner whorl of the perianth, the two lat- 
eral members are usually small and of the same shape as 
those of the outer perianth members, whereas the median 
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