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282 FERTILIZATION OF FLOWERS BY INSECTS. 
the process of their fecundation, because his theory of natural 
‘selection, according to which only useful qualities can be fixed and 
preserved in living things, placed him in a condition to infer from 
simple inspection of the flowers, the details of the fecundative 
process. 
As far as concerns the Orchis of our fields, Darwin had come 
to the conclusion that the insects visiting them might suck 
the honey enclosed between the inner and outer membranes of the 
spur, piercing the latter with their proboscis ; that such an opera- 
tion required the precise time necessary for the viscous stalks 
of the pollen-masses to attach themselves firmly upon the heads of 
the insects; and that the time occupied by the pollen-masses 
securely attached to the insects in becoming depressed upon their 
stalk. so as to be able to rub against the stigma, corresponds 
nearly to the time employed by the insects in visiting one plant 
and passing to another. In this way, intercourse between two 
individuals would necessarily take place. 
However, when we consider the immense number of such Orchids 
in the meadows, and reflect that insects have to perform several 
. Operations in order to fecundate them, it seems strange that they 
should never havé been surprised at work by any one. Fortu- 
nately, I am able to fill up this gap and at the same time fully 
confirm Darwin’s conclusions. 
Towards the close of last spring I had taken a good many Bombi 
and some honey bees with several masses of pollen upon their 
heads, and I saw a Bombus sylvarum fly to the flowers of Orchis 
Morio, stick its proboscis into the spur and fly away with pollina- 
ria upon its head. On another occasion, I saw at a distance a 
Bombus lapidarius fly to the flowers of Orchis latifolia ; and I also 
saw a dipterous insect, Volucella bombylans, with the pollen-masses 
of Orchis maculata upon its head. However, during the spring I 
was not able to observe these insects closely enough to note exact- 
_ ly their movements and deportment. 
But subsequently, on the sixth of this month (May, 1869) upon 
the heights of Stromberg, very abundant in Orchis, both I and 
my son Hermann were enabled with ease, and close at hand, 
to observe many Bombi at work. At a place full of Orchis mascula 
we saw a Bombus which appeared to be B. terrestris fly to the low- 
ermost flower of a spike of this Orchis. It inserted its head into 
the flower, remaining about four seconds, and then withdrew it with 
