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.
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