The cowslip differs so conspicuously in general appearance from the primrose, that nothing need here be said with respect to their external characters. (2/2. The Reverend W.A. Leighton has pointed out certain differences in the form of the capsules and seed in ‘Annals and Magazine of Natural History’ 2nd series volume 2 1848 page 164.) But some less obvious differences deserve notice. As both species are heterostyled, their complete fertilisation depends on insects. The cowslip is habitually visited during the day by the larger humble-bees (namely Bombus muscorum and hortorum), and at night by moths, as I have seen in the case of Cucullia. The primrose is never visited (and I speak after many years’ observation) by the larger humble-bees, and only rarely by the smaller kinds; hence its fertilisation must depend almost exclusively on moths. There is nothing in the structure of the flowers of the two plants which can determine the visits of such widely different insects. But they emit a different odour, and perhaps their nectar may have a different taste. Both the long-styled and short-styled forms of the primrose, when legitimately and naturally fertilised, yield on an average many more seeds per capsule than the cowslip, namely, in the proportion of 100 to 55. When illegitimately fertilised they are likewise more fertile than the two forms of the cowslip, as shown by the larger proportion of their flowers which set capsules, and by the larger average number of seeds which the capsules contain. The difference also between the number of seeds produced by the long-styled and short-styled flowers of the primrose, when both are illegitimately fertilised, is greater than that between the number produced under similar circumstances by the two forms of the cowslip. The long-styled flowers of the primrose when protected from the access of all insects, except such minute ones as Thrips, yield a considerable number of capsules containing on an average 19.2 seeds per capsule; whereas 18 plants of the long-styled cowslip similarly treated did not yield a single seed. The primrose, as every one knows, flowers a little earlier in the spring than the cowslip, and inhabits slightly different stations and districts. The primrose generally grows on banks or in woods, whilst the cowslip is found in more open places. The geographical range of the two forms is different. Dr. Bromfield remarks that “the primrose is absent from all the interior region of northern Europe, where the cowslip is indigenous.” (2/3. ‘Phytologist’ volume 3 page 694.) In Norway, however, both plants range to the same degree of north latitude. (2/4. H. Lecoq ‘Geograph. Bot. de l’Europe’ tome 8 1858 pages 141, 144. See also ‘Annals and Magazine of Natural History’ 9 1842 pages 156, 515. Also Boreau ‘Flore du centre de la France’ 1840 tome 2 page 376. With respect to the rarity of P. veris in western Scotland, see H.C. Watson ‘Cybele Britannica’ 2 page 293.)