POLLINATION OF THE BRITISH PRIMULAS. 135 
effected normally by night-flying moths*. Various considerations go to 
support this view. 
In the first place, Darwin sayst that one of his sons actually caught a 
moth, Cucullia verbasci, in the act of sucking a Cowslip flower—an interesting 
and, I believe, unique observation f. 
Seeondly, the flowers of two of the Primulas under notice (namely, the 
Primrose and the Oxlip) are pale yellow—a colour which is exceptionally 
conspicuous by night and is characteristic of many flowers which are 
pollinated habitually by night-flying moths; whilst those of the third 
species (namely, the Cowslip, which probably depends more on the visits of 
day-flying insects) are of a deep yellow. 
Thirdly, all three species possess nectar-guides (the five orange-brown 
spots forming the “eye” of the flower), and these are of a type usual in 
flowers pollinated habitually by night-flying insects—that is to say, promi- 
nent, but not sharply defined like the narrow lines seen on the petals of 
many day-pollinated flowers. 
Fourthly, the scent of most, if not all, flowers which are pollinated 
habitually by night-flying moths becomes stronger after dusk—of course, to 
attract the moths which fly at that time ; and this is the case with our 
Primulas |. I was particularly struck with this fact on the evening of 
22nd April, 1916, which was warm and still. About 6 o’elock, just as it 
was getting dark, I went into an old clay-pit, “carpeted ” with Primroses 
in full flower, in a wood adjoining my garden, when I was struck at once and 
most forcibly by the strong scent of the Primroses, which permeated the 
whole atmosphere. This it certainly does not do during the daytime, or to 
a very limited extent only ; for the day-scent of all the three species is quite 
faint. On the other hand, it was probably the strong dusk-scent of the 
Primrose which attracted the numerous small creatures Mr. Dallman observed 
visiting the flowers after dark **. 
* See ante, p. 107. 
+ Journ, Linn. Soc. Bot. x. (1869), p. 423, and ‘Forms of Flowers, p. 22 (see 
ante, pp. 108, 128). 
t He omits to record whether the insect was caught during the day or the night, but 
says that he found on its proboscis an abundance of pollen of both forms. Sir Francis Darwin 
informs me that it was not he, but probably his brother, the late Sir George Darwin, an 
enthusiastic entomologist, who caught the insect. 
§ Unfortunately, I omitted to observe how long the scent continued to be so strong. If to 
attract moths which fly only for a short time after dusk (as many do), probably it did not 
continue long. 
| Prof. Boulger has said of the Primrose (Nature Notes, xv. (1904), p. 85) that it is 
«í somewhat more scented, I think, at dusk or by night.” — 
@ It is possible that the faintness of the day-scent of the Oxlip is accountable for the fact 
that many Continental botanists (e.g., Grenier & Godron, * Fl. de France,' ii. 1850, p. 448) 
have described its flowers as scentless (“inodore "). 
** Journ. of Botany, lix. (1921), pp. 820-822, &c. (see ante, p. 114). 
