136 MR. MILLER CHRISTY ON THE 
There are yet other facts which have evidential value in this connection. 
It may be noted that, in the genus Primula (comprising, according to Pax 
& Knuth*, 208 species), a very large majority of the species have brightly- 
coloured flowers (usually red, pink, mauve, purple, or some combination of 
colours), while the very-small minority (certainly not 5 per cent. of the 
whole) have light-coloured flowers (white, whitish-yellow, or yellow). Further, 
it may be noted, that, of these few which have light-coloured flowers, 
nearly all are species which flower (unlike the majority) in early spring. 
These early-flowering species, eight in number, constitute a well-defined 
section of the genus (the * Sectio Vernales" of Pax & Knuthf), and all 
of these, with two exceptions, have yellow flowerst. It is clear, therefore, 
that in this genus, yellow flowers and early-spring flowering are associated. 
Now, there can be no reasonable doubt that all the brightly-coloured species 
which flower during late spring and summer are pollinated by long-tongued 
humble-bees, butterflies, and other day-flying insects, for their comparatively- 
dark colour renders them very inconspicuous in the darkness of the night. 
These facts, then, go far to justify the assumption that the few exceptional 
members of the genus which have ye!low flowers and flower in the early 
spring (which include the three species in question) are intended for 
pollination by night-flying insects ; and there are (in Britain, at any rate) no 
such insects except moths. 
Moreover, there is, indigenous to Britain, a considerable number of species 
of moth (chiefly hybernating species) which come abroad at the early season 
of the year when the three species of. Primula concerned are in flower—say, 
roughly, from 15th March to 15th May. Dr. R. C. L. Perkins, F.R.S., has 
been good enough to prepare a list of some thirty-five species of Noctuidæ 
and Geometridze which are known to do so. From this, I hoped I might be 
able to ascertain easily whieh species were those most likely to be concerned 
in the pollination of the flowers of our British Primulas. I soon found, 
however, that owing to the almost-complete lack of records of the tongue- 
lengths of British insects (already referred to ||), the list was of no help in 
this direction, inasmuch as there was not on it a single inseet of which the 
tongue-length was known. In this dilemma, I received kind help from 
* Primulaces (in Engler’s ‘ Pflanzenreich, vol. 22) (1905). 
+ Op. ett. pp. 47-65, 
} They are P. pseudo-elatior, elatior, leucophylla, acaulis, officinalis, heterochroma, amena 
(purple) and Julie (red). 
$ For instance, P. farinosa, a pink-flowered summer-flowering species, is known to be 
visited by insects very freely by day. Müller notes (Fertil. of Flowers, p. 386) no fewer 
than 48 species of Lepidoptera which visit it on the Alps, and a number of bees which visit 
it in North Germany. 
|| See ante, p. 125. 
