394 REV. GEORGE HENSLOW ON THE 
though * trimorphic,” is widely dispersed, and thus affords an exception to the general 
rule. Epilobium angustifolium, N. and W. Asia. E. hirsutum, N.E. Af. Menyanthes 
trifoliata (dimorphic ?), Jap. Thymus serpyllum, Sib., W. Asia, Greenland, Jap., N.E. Af. : 
Nepeta Glechoma, Jap., Hong. Stachys Betonica, Mad., N. Af., W. Sib. Echium plan- 
tagineum, Mad. 
This list is not complete, but it comprises the chief of those which I have ascertained 
from the same floras which have furnished the much more numerous list of widely dis- 
persed self-fertilizing British plants. I need hardly add that the majority of our conspicu- 
ously flowering plants are not extra-European at all, or are, at the furthest, in W. Asia. 
Sir J. D. Hooker observes, in his essay ‘On the Flora of Australia,’ p. 13 :— 
* Those Classes and Orders which are the least complex in organization are the most widely distributed, 
that is to say, they contain a larger proportion of widely diffused species. Thus the species of Aco- 
tyledons are more widely dispersed than those of Monocotyledons, and these again more so than those of 
Dicotyledons." | 
To this I think may now be added that self-fertilizing and anemophilous flowering 
plants are more widely dispersed than those requiring insect-agency. | 
Mr. T. Comber, in his interesting papers * on the dispersion of British plants, remarks. 
on those having inconspicuous flowers :— 
_ * They [whether assumed to be early progenitors or degradations] will have attained a greater age as - 
species, and having had a longer time for their migration, we may expect to find that they have also a 
high degree of dispersion, which will be most conspicuous in Orders that are entirely composed of such 
plants. This is found to be true, and that plants with white flowers are more widely dispersed than those 
with coloured. Further analysis shows that plants with flowers sometimes white and sometimes coloured, ` 
as wood-anemones, many violets, thistles, and campanulas, are intermediate in this respect, having a - 
more limited range than those whose flowers are always white, and, on the other hand, a more extended : 
range than those with flowers always coloured." 
He here attributes the dispersion of white-flowering plants to the fact of their greater 
antiquity. No doubt this may be justly regarded as a factor in the phenomenon; but 
the one I lay most stress upon is the fact that they are self-fertilizing. The other 
peculiarities of such plants, viz. of having white or pale-coloured flowers, and in being 
usually annuals or biennials, are secondary conditions correlated with self-fertilization. 
It has been observed that white varieties are hardier than coloured ones, and this may be 
correlated with wide dispersion; and there is the fact that self-fertilizing (wild) plants 
are best capable of withstanding extreme climates, as noticed above by Berkeley. A. 
writer (anonymous) in the * Gardeners' Chronicle, for Sept. 22, 1877, found the white | 
variety of Solanum Dulcamara, but no other form, growing from 200-300 feet above the 
sea in Scotland, and attributes this to its greater hardiness. Again, Mr. Comber reminds | 
us that DeCandolle shows that monocarpie (annual and biennial) plants are more widely 
dispersed than perennial, while annuals have a more widely extended range than biennials. | 
Now this is completely correlated with self-fertilization, or else with anemophilous 
states. : 
=% Journal of Botany, N. S., iii, p. 284 (1874). — 
