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BOTANICAL MUSEUM LEAFLETS 
HARVARD UNIVERSITY 
CampripGce, Massacuusetrs, Jury 1, 1937 
POLLINATION OF ORCHIDS 
THROUGH PSEUDOCOPULATION 
BY 
Oakes AMES 
ILLUSTRATIONS BY BLANCHE AMES 
WITHIN comparatively recent years, biologists have 
been made aware of a peculiar relationship between cer- 
tain orchids and the hymenopterous insects which polli- 
nate them. A wholly unexpected trend in biological 
behavior has been revealed and it has been proved that 
the motives leading to pollination are much more com- 
plex than formerly had been supposed. It is now known 
that certain insects are attracted by orchids for a purpose 
wholly apart from the search for food and that there are 
aspects of pollination presenting new and practically un- 
explored fields for research. 
The historical approach to the subject of the pollina- 
tion of orchids carries us back to what may be termed 
the beginning of the rational epoch in natural history, 
when guess-work and philosophical speculation were 
steadily giving ground to critical studies and reasoned 
research. Indeed, it was the mystery surrounding the 
methods of fecundation in the Orchidaceae that impelled 
Robert Brown to review the theories that had been pro- 
pounded from 1760 down to 1831 and to examine the 
matter by actual observation. In the Transactions of the 
Linnaean Society for 1833 appeared Brown’s famous 
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