AND THEIR MORPHOLOGY. 129 
question it should not be forgotten that both powers, although 
they admit of being considered separately, may be only conse- 
quences of the same physiological quality. 
From the above it is made evident that the fecundation of the 
female flower must take place by means of the pollen of the male 
flower, as in other plants with distinct sexes. As fruit on this 
plant is extremely common, it is impossible to attribute it to any 
other agency than that of insects. And here I have had occasion 
to verify the supposition of Darwin to its fullest extent. 
The female flower opens when still comparatively young, as 
already mentioned. The male flower emits a peculiar smell 
about twenty-four hours after opening, and the antenns assume 
their greatest irritability at the same time. A large humble-bee, 
noisy and quarrelsome, is now attracted to the flowers by the 
smell, and a great number of them may be seen every morning 
for a few hours disputing with each other for a place in the inte- . 
rior of the labellum, for the purpose of gnawing off the cellular 
tissue on the side opposite to the column, so that they turn their ` 
backs to the latter. As soon as they touch the upper antenna of 
the male flower, the pollen-mass, with its disk and gland, is fixed 
on their back, and they are often seen flying about with this pecu- 
liar-looking ornament on them. I have never seen it attached 
except to the very middle of the thorax. When the bee walks 
about, the pollen-mass lies flat on the back and wings; but when 
the insect enters a female flower, always with the labellum turned 
upwards, the pollinium, which is hinged to the gland by elastic 
tissue, falls back by its own weight and rests on the anterior face 
of the column. When the insect returns backwards from the 
flower, the pollinia are caught by the upper margin of the 
stigmatic cavity, which projects a little beyond the face of the 
column; and if the gland be then detached from the back of the 
insect, or the tissues which connect the pollinia with the caudicle, 
or this with the gland, break, fecundation takes place. I have been 
an eye-witness only of the first event; I conceive, however, the 
possibility of the other. 
I have tried to represent the above by a sketch (Pl.-IX. figs. 1, 
2,3). That the insects are attracted at first by the smell of the 
flower I take from the fact that the same insect visits Coryanthes 
macrantha, Stanhopea grandiflora, and Gloxinia maculata, all three 
of which have the same perfume. But the smell probably only 
gives notice to the insects; the substance they really come for, 
in the case of these Orchids, is the interior lining of the labellum, 
M 2 
