80 
on the 15th of June last. All the plants when taken up were well set 
with large flower-buds, which opened a week later and lasted un»til 
the middle of July. During that time I watched about one hundred 
and thirty flowers out of a total of two hundred and ten during their 
period of flowering, and noticed with much interest the great sensi- 
tiveness of the stamens, which are very numerous in this prickly- 
^fP^ j^ ^^ ^^ ^ 
pear 
The window-boxes have an eastern exposure, and consequently 
the sun passes out of view about one o'clock in the afternoon. 'J'he 
flowers opened about seven in the morning and closed shortly after 
two, or about an hour after the sun passed away, although they would 
have remained open two hours longer under its direct influence. 
Durmg sunshine each flower would open for two consecuive 
days, but_ in cloudy weather for only one day. On the first day of 
the opening of a flower the pointed stigmas were hardly separated 
sufficiently to admit of the passage of a small-sized straw. But on 
the following day, under the influence of the sun's rays, the stigmas 
expanded to their fullest capacity. 
Less pollen was observable on the anthers during the first than on 
the second day of flowering. Or, in other words, the longer a flower 
remained open the greater the number of pollen grains that were 
discharged from the anthers. And yet fructification seems to have 
been effected in nearly every case in which a flower opened for either 
one, or two days in succession. I now count about one hundred and 
ninety promising fruits. 
The beautiful lemon-colored flowers of this Opuntia attracted 
many honey-bees, and their movements I carefully watched with a 
pocket -lens in hand on every fair or sunny day. A bee would alight 
on the mass of anthers, then push its forelegs down among the fila- 
ments, which were sufficiently compressed to admit of the body of 
the insect passing more readily down to the nectaries of the flower. 
As soon as the filaments were released from the grasp of the in- 
sect, the stamens were suddenly thrown against the pistil, from which 
they sjowly receded to their former position. I should judge that 
sometimes more than a dozen stamens were thus rudely seized by a 
honey-bee in its endeavor to reach the nectaries, the insect frequently 
makmg the circuit of the whole arrangement of stamens, and always 
coming up again to the surface of the anthers before taking a second 
plunge to the base of the corolla. Although the feet (legs) of the 
insect were covered with masses of pollen after visiting a flower, yet 
at no time do I remember seeing one crawl over the stigmas, 
whereby fertilization might have been insured. It seems to me 
mat the pollen grains are thrown between the stigmas after the 
sudden movement of the stamens following the retreat of an insect. 
^ 1 have also noticed flies of several species visit these flowers on a 
T.l ''cf ^^ ' ^^'^ apparently being followed by the same movements 
of the filaments. On the 12th of July, I was collecting in Pelham- 
yille, Westchester County, and there also observed a few late-flower- 
mg specimens of Opuntia^ vulgaris, on one of which I observed a 
large humble-bee going for his nectar ; and how he did make the 
dust (pollen) fly! 
