1892. Evolution in Methods of Pollinatton. 75 
When cross-fertilization by means of insects has become as- 
sured, the color, time of flowering, fragrance, the length of 
the corolla tube, the form and, position of the petals and 
sepals, all have reference to time of flight and character of the 
especially invited guests. Every hair has a meaning. Every 
curve is an adaptation. The power of self-fertilization, at 
first indispensable, may become useless.: A struggle for exis- 
goes to the ground. So cross-fertilization is, as a rule, alone 
possible among the majority ‘of orchids, some Composite, 
some species of Salvia, Aconitum, Corydalis, Dianthus, Malva 
and others. Many changes, progressive and retrogressive, 
are still going:on. - It is known that the honey of more than 
one hundred and thirty-two flowers can be plundered from 
outside without the touching of the stamens or stigma. In 
these cases at least, perfection has, not been reached; but the 
wonderful contrivances to prevent the entrance of useless 
guests, such as hairs on the calyx, corolla or stamens, slip- 
periness of the corolla, a pendent position of its tube, or the 
accumulation in the petals of matters offensive to insects, show 
that some species are on the high-road to it. 
So much for flowers; but there are weeds, hundreds of them, 
widespread and homely. Many, perhaps all, of those which 
have the rudiments of calyx and corolla are degraded forms, de- 
scendents of species once fertilized by insects, but which, because 
of the extinction of the particular ones on which they either 
depend, or because they have spread into regions where these 
insects are not, or because thrown into the shade by the super- 
‘oF attractions of their neighbors, have been obliged to resort 
again to wind agency (Plantago?), or to adapt themselves to 
almost exclusive self-fertilfzation (Veronica hederefolia). In . 
either case there is no longer need of aftractive organs and the 
petals have accordingly been reduced. The evil effects of 
Continued self-fertilization may have had a share in this re- 
sult; but probably not to a great extent, for such effects will 
be largely counteracted by the wide dissemination so character- 
a of weeds, by which these low forms are exposes to great 
variation of climatic conditions. The loss is then of beauty, 
not of Strength. Change of environment seems often to have as 
Teneficial results as cross-fertilization in the stimulation of the 
Sih rent and the production of varieties. The degradation 
» as elsewhere, is only a peculiar form of adaptation. 
