286 FERTILIZATION OF FLOWERS BY INSECTS. 
again to the small aperture, and then again climbed up with no 
‘better success than before. Then, after a short pause, it ran with 
greater impetus to one of the small apertures (to the left) and 
using all its strength, at length succeeded in pressing down the 
lip and pushing its head, thorax, fore legs, and finally its whole 
body through this aperture, and so was again at liberty. In this 
passage, its right shoulder rubbed against the anther overhang- 
ing the aperture and carried away a good deal of the pollen. 
The flower of Cypripedium, then, must be considered as a trap 
for Andrenas which enter it, allured by a sweet exhalation, and the 
minute drops of honey exuding from the apices of certain hairs in 
the lip. If an Andrena visits this snare during the warmer hours 
of the day, that is to say, when it possesses its maximum vital 
energy, it easily succeeds after a few minutes in freeing itself 
from its prison, but not without first getting some pollen upon its 
back which will fecundate the stigma of the next flower it visits. 
But if it is caught in the cool of the evening, it must perforce 
make up its mind to take lodgings there for the night, and be con- 
tent to escape from its unwelcome quarters during the warm hours 
of the next day.* 
If small Andrenas falling into this trap have not strength enough 
to push aside the lip so as to escape through the small apertures, 
*The structure of the flowers of yaiany Tetel to the mode in which pro 
miscuous intercourse is effected b ns of insects, has been studied, in order of 
i in .M pag 
rtai sects wh 
holes of the sac, became covered with pollen which was then communicated to the 
pe 
Gra m after, from an examination of some American ine concluded s 
Prik iana was effected by 
leaving it covered with pollen by the small ones. 
In 1866 I examined some exotic Cypripedia in Florence, and, though ignorant of 
Gray’s observations, reached the same conclusion (On the arrangements for fecund. 
of anthoc., plants 1867, p. 20, 22 
The next ae ar E. Müller (Beobacht. an West fiilisch. Orchidera p.1-6), sean 
the dh of m Conjectures, observing and a 03 mode of action of certai 
andrenas in q f C. 
In 1868 and 1869, having had occasion to study anew ait ow wers of some foreign Cy- 
pripedia (C. barbatum and others), I observed the manner in which large flies are 
imprisoned in them. It should be noted that not unfrequently in the Boboli botani 
gardens the ovaries of Cypripedia ripen, without Sout, in aaa ake of the visits 
y Darwin (notes on the sass of Orchids, 1869, p. 16 and 17) cited the 
y, myself, and Müller, fully admitting the re- 
