OF WASHINGTON. 151 
Yucca much, too, that has not shown the keenest penetration nor the 
strictest accuracy. But, in candidly admitting his errors when shown to 
be wrong (as he has done to the writer and, I have reason to believe, to 
Mr. Hulst, who sought his support in the belief here combated), he has 
proved himself to be the true naturalist. I am familiar with his experi- 
ments, having witnessed the results, and can best express my own opin- 
ion by quoting from a letter from the late Dr. G. Englemann (written Jan. 
10, 1881), in which among other things he says: * * * "As to Mee- 
han's operations I have seen myself the fine, large, well-filled pods of 
Yucca angustifolia raised by him by his artificial method. He says he 
punches an anther into the stigmatic cavity. Whether he or anybody 
else could distinguish whether the pollen adheres only to the papillose 
(not stigmatose) apex or gets into the liquor that fills the cavity when the 
stigma is ready to conceive, is a question (or no question) !" Meehan's 
experiments were made on a 'species in which, as I have elsewhere shown, 
the stigma is shorter and the stigmatic liquor more abundant than in 
Yucca filamentosa, and it may be that for these or other reasons it is more 
easily pollinized by hand or by other means than by Pronuba. But I have 
followed up his experiments and made many others during the past seven 
years, onfilamentosa and aloifolia, with results that convince me that ap- 
plication of the pollen to the papillose apices only is not sufficient to in- 
sure fructification, at least in those species. My experiments have been 
made in the afternoon^ evening, and morning; with flowers one day, two 
days, and three days after opening; with pollen from the same flower or 
from other flowers either on the same or other racemes ; by touching the 
mere apices with anther or brush, and by forcing the pollen by either con- 
veyance into the stigmatic tube. In these experiments, which have not 
yet been published, and which it is unnecessary to detail here, I have 
endeavored to guard against all influences, such as the condition of 
the plant and the weather, which might affect or vitiate, the results. These 
may be summed up thus : 
(1) Dr. Engelmann's limit of time during which fertilization may take 
place must be extended so as to include the second evening, and even the 
second morning, after the opening of the flower. 
(2) No seed has been produced by merely touching the apices of the stigma 
with the pollen, though partial fertilization may take place and cause the 
growth of the fruit for a varying period, generally only three or four days. 
When the pollen is thrust into the tube (the mode of conveyance making 
little difference) fertilization is much more certain, but even here is rarely 
sufficient to produce ripe seed, the upper part of the pod often filling well, 
but the basal part not filling, and at last withering so that the fruit ulti- 
mately falls off before ripening. 
The conclusion is inevitable that angustifolia is more susceptible to arti- 
ficial pollination than the species which I experimented with, and that 
Pronuba far excels man in the perfection with which she performs the act. 
She has the power of fertilizing all "the ovules, at which nb one will wonder 
who has carefully watched her, because the act of pollination is normally 
