332 REV. GEORGE HENSLOW ON THE 
regain, or at least acquire, the power of self-fertilization. The probable immediate causes ` 
will be dwelt upon more fully hereafter. f 
Hence we see, on the one hand, that flowers adapted for intercrossing by insects may 1 
become self-fertilizing in their absence, and yet retain their conspicuousness. On the 
other, as I surmise, they may in the course of many generations give rise to self-fer- | 
tilizing forms (species) by the retention of an arrested corolla and other structural 
alterations; as will be referred to in the case of Zpilobiwm parviflorum as compared with | 
E. hirsutum, and species of Spergularia Ke, l 
There would seem to be two other alternatives which may happen to such plants on the © 
failure of insects to visit and cross them: the one is to become anemophilous or wind- ! 
fertilizing. Such appears to be the case with Poterium, Littorella, Plantago, the Amen- f 
tifere (mostly), Grasses and Sedges. The other alternative is to perish entirely. And — 
this last has, I suspect, largely taken place under migration, as will be shown more fully — 
hereafter: ! 1 
A propos of the connexion between the conspicuousness of flowers and the presence of | 
insects, Sir J. D. Hooker informs me that, speaking generally of the Arctic flora, it is 
remarkable for its many conspicuous flowers when compared with the Antarctic, and 
that the former is associated with insects, whereas the latter has but comparatively few. ` 
The Rocky Mountains would seem to illustrate an intermediate condition; for thus 
speaks Mr, Meehan (‘ Gardeners’ Chronicle,’ Sept. 11, 1875, p. 327):— | 
“ The flowers of the Rocky-Mountain region are beautifully coloured; but Fremont pathetically de- 
scribes the solitary Bee that rested on his shoulder at the top of Pike's Peak. On my first visit the. 
comparative absence of insects proved very annoying to the entomologists who accompanied me. It 
was a frequent subject of conversation, whether Fremont’s Bee was not apocryphal; and though, on. 
a visit some years later, some Humble-bees on Polygonum Bistorta, on Gray’s Peak, enabled me to do 
justice to the veteran explorer, the incident shows how rare such insects are. Indeed, the paucity of 
animal life of all kinds in the Rocky Mountains is well known; but there is no more scarcity of seed. 
in the coloured flowering plants than in similar ones elsewhere." 
Mr. Meehan also justly calls attention to the fact of spring flowers being abundant, 
but blossoming at a time when few or no insects are about; yet they all, without any 
remarkable exception, seed well. 
4. vill, Plants may become self-fertilizing on the reduction of temperature. This has 
already been alluded to in speaking of flower-buds not opening, and so becoming self- 
fertilizing in the autumn and winter. But besides such cases of indigenous plants, 
Mr. Darwin records the fact of Eschscholtzia californica being physiologically self-sterile 
in Brazil, but which, when transferred to and grown from seed in England, became self- 
fertile. Moreover, when transported to Germany, it again became self-sterile, as also 
did English-grown plants when sent to Brazil Similarly, Abutilon Darwinii, * which 
is self-sterile in its native home of Brazil, became moderately self-fertile in a single 
generation in an English hot-house.". In allusion to the Poppy, Papaver, he found 
some plants are self-sterile during the early part of the year, but later in the season 
become self-fertile. ** P. vagum produced plenty of capsules in my garden when 
insects were excluded, but only late in the season" (p.108). Mr. Meehan, as quoted 
