YUCCA MOTH AND YUCCA POLLINATION. 103 
the genus Habenaria, for instance, we find flowers which 
in some cases strongly resemble butterflies; a separate 
pocket for the nectar; the pollen bound together in masses 
by elastic threads, so as to lessen the chance of loss; the 
base of the stamens forming flattened sticky discs placed 
in the best possible position for adhering to the head-parts 
of a moth endeavoring to reach the nectar. In all these 
features and others that might be mentioned, there is 
remarkable adaptation; and the flowers of many orchids, 
as they unfold, seem not only to invite but to court and 
- crave the intervention of some scaly-winged marriage-priest 
‘¢of glorious color and glistening eye,’’ who shall at once 
procure a suitor and perform the nuptials. Yet here we 
have the adaptation of the plant only, and except in a few 
instances, as, for instance, in that Madagascar orchid, 
Angraecum sesquipedale, where the nectary is so deep that 
_ its nectar can be reached only by a moth (like Macrosila 
cluentius) with a very long tongue, our orchids are not 
dependent for pollination on any one Lepidopterous species, 
- but may be aided by many which have tongues of sufficient 
length. 
CONNECTION OF YUCCA AND PRONUBA. 
There are, in fact, few plants which are dependent on a 
single species for pollination. So far as I know, the 
Yuceas furnish the only instance of this kind, for they 
actually depend on some particular species of little white. 
moths belonging to the Tineina and to the genus Pronuba. 
The Yuccas are a very interesting genus of lily-like plants, so 
familiar to everyone in our public and private gardens that 
I need not say very much aboutthem. There are numerous 
species and even sub-genera, but they are all characterized 
by anthers not reaching anywhere near the stigma, so that 
fertilization unaided can take place only by the merest 
accident. In other words, the stigmatic tube is nowhere 
within reach of the stamens, and the pollen either remains 
attached to the open and withered anthers or falls and 
