FERTILIZATION OF FLOWERS BY INSECTS. 285 
onds is sufficient to stick the pollen-masses firmly upon the heads 
of the insects, and any one can easily convince himself of the 
fact by introducing into the flower a sharpened pencil, and holding 
it for three or four seconds when, upon withdrawing it, pollen- 
masses will be found adhering to it. It will also be found that in 
about forty seconds after drawing it out, these masses will have 
completed that movement of declination by virtue of which they 
can come in contact with the stigma. Now, as a bee, from what 
we observed, does not remain on a given spike longer than twenty 
or twenty-two seconds, it is clear that it cannot fecundate it with 
its own pollen, but only with that of spikes previously visited. 
On the 11th of May, 1869, in the neighborhood of Lippstadt 
near Overhagen, I repeatedly saw bees effecting the fecundation 
of Orchis latifolia, but I observed nothing new, or in any way diff- 
erent from what I ia in the case of Orchis mascula. 
Towards the close of last year I published in the acts of this 
Society an observation made in May, 1867, upon the fecundation 
of Cypripedium, which was in many respects incomplete because 
made under unpropitious circumstances, although I succeeded with 
the aid of the Darwinian theory, in completely explaining the part 
the different floral organs play in securing the fecundative process. 
But on the 16th of May, 1868, in the same locality, I was able to 
make a greater number of observations, and confirm all my con- 
clusions. This place which was of limited extent had only six 
flowers of Cypripedium. Passing and repassing in the examina- 
tion of the slipper-like flowers peculiar to this plant, I found in 
one of them, which half a minute before was empty, an Andrena 
pratensis which by its violent agitation could be perceived at the 
distance of several feet. Visibly disquieted by its imprisonment 
it tried at least twenty times to climb up the walls of the slipper, 
but these are so contorted, and of such a shape, that after every 
attempt the Andrena slipped back again into the flower. Finally, 
it retired to the base of the flower and pushed its head into one of 
the two small apertures there; but this being too narrow, it at- 
tempted to scale the walls anew, and not succeeding, ran back 
come upon organs or parts of organs, Novae really merit this a ae it does not 
seem to me applicable here. I ascri to Orchids an illusory spur, once 
me ae but now now dry, and I eink th that is the better view. It is in favor of thi this 
+ ee EA 
and ofer an incredibly small eshte, of per em pollen-masses and fecundated 
ovar: 
