SELF-FE RTILIZATION OF PLANTS. (829 
this plant has a paler yellow colour than the intercrossing form, and, moreover, the red 
tint at the base of the latter is also wanting. 
Fumaria capreolata, var. pallidiflora, is, according to Müller's belief, restricted to 
self*fertilization *. 
A fact connected with white varieties is that they generally transmit their colour much 
more truly than any other variety (Anim. and Pl. under Domest. ii. p. 20), and rarely 
vary into any other colour. Mr. Darwin says he has found the white varieties of 
Delphinium Consolida and of the Stock are the truest; so is the white var. of the Sweet 
Pea according to Dr. Masters. Now the annual species of Delphinium are easily self- 
fertilized, though by Mr. Darwin’s experiments are not quite so fertile as when crossed, 
and the Sweet Pea is highly self-fertile. And when we remember that the most widely 
dispersed British plants are white, and also self-fertile, we seem to arrive at the clue 
to the fact stated at the beginning of this paragraph, namely, that white colour is cor- 
related with a more or less facility to self-fertilize. Hence the stability of the colour; 
for Mr. Darwin has shown how any strain can probably be retained by perpetual self- 
fertilization, all crossing being carefully prohibited. 
4. v. Self.fertilization may be secured by the flowers closing after expansion. It has 
been suggested that some flowers close at such periods of the day or night when they 
willnot be visited by their proper insects, so as to preserve the nectar or honey. I 
would, however, suggest another and much more important object as being gained, and 
that is self-fertilization. Buttercups which are self-fertile, as Ranunculus acris, which 
Mr. Darwin records as producing plenty of seeds under a net, cannot fail to press the 
stamens down upon the pistil as they close, and thus secure the impregnation of the 
. earpels. 
Many flowers, e. g. Mesembryanthema, close as soon as the direct sunlight ceases to 
shine upon them, but long before insects would fail to see and visit them. Our own 
Anagallis arvensis, though very conspicuous, may be also aided by the rapid closing of 
the corolla; it appears, however, to be self-fertilizing irrespective of that fact. The 
order of development of the whorls is calyx, stamens, pistil, corolla. The pistil overtakes 
the stamens, and the stigma matures at the dehiscence of the anthers which cluster 
round it, especially by the closing of the corolla. Pollen-tubes were easy of detection. 
Erythrea Centaurium and Chlora perfoliata both appear to facilitate or bring about 
self-fertilization by the corolla folding round the anthers and stigmas which are thus 
brought into immediate contact. Other plants close in the evening. Light would seem 
to be the chief cause at work; for flowers which have closed at dusk will often reopen 
in artificial light, as do Crocuses. Mr. T. Meehan has arrived at exactly the same con- 
clusion as myself, our observations having been quite independent. (‘The ` Sleep of 
Plants’ as an Agent in Self-fertilization," Proc. of Acad. of Nat. Sc. of Philadelphia, 
1876, p. 84.) 
* Mr. J. Traherne Moggridge drew attention to the fact that the colour of the corolla heightened after fertiliza- 
tion (* Nature, April 2, 1874). This raised a discussion as to the use of colours not being solely for insect agency. 
May not the interpretation be that as the ovule develops into seed, the heightening of the corolla was an accidental 
correlation with the increase of nourishment now determined to the flower? 
