CCVII. — THE COWSLIP. 
Primula veris Linne. 
T HE Order Primulales has usually polysymmetric, pentamerous, perfect flowers 
with epipetalous stamens and a one-chambered ovary with basal or free-central 
placentation. The number of parts in each floral whorl is not always five, the flowers 
are sometimes unisexual, and very frequently there is only one whorl of stamens and 
they are opposite to, instead of alternating with, the petals. The Order includes 
two Families with British representatives, the Primulacea and the Plumb aginaceie. 
The Primu/acea are a Family of herbaceous plants well known for the great beauty 
of their copiously produced flowers, though of small economic importance. There 
are nearly thirty genera and four hundred species, nine genera and seventeen species 
being British. The group, though practically cosmopolitan, belongs mainly to the 
Temperate and Arctic regions of the Northern Hemisphere, many of the species 
being sub-alpine or alpine, reaching in various latitudes to the confines of perpetual 
snow. Most of them are low-growing perennials with simple, exstipulate leaves, 
bearing perfect flowers on scapes, or peduncles rising direct from an underground 
stem. The flowers are often relatively large, mostly secrete honey, and exhibit 
those bright and clear shades of colour so characteristic of mountain plants. The 
calyx is gamosepalous, persists in the fruit stage, and, except in the Brookweed 
(, Samolus ), is inferior ; and the occasional presence of a whorl of staminodes explains 
the position of the stamens each in front of a petal. An outer whorl is clearly 
aborted or suppressed. It is, however, a remarkable fact that, in the early stages of 
the development of the flower, the petals originate later than, and as outgrowths 
from the outer sides of, the stamens. 
Many members of the Family have dimorphically heterogonous flowers : 
different individuals, that is, produce flowers differing in the relative positions of 
the anthers and stigma — an arrangement which was shown by Darwin to be accom- 
panied by marked physiological characters tending to secure cross-pollination. One 
plant will have a long style, so that the stigma stands at the mouth of the corolla- 
tube, while the anthers are inserted half-way down it : the other form will have a 
short style, so that the stigma is half-way down the tube, while the anthers are at its 
mouth. The Nottingham weavers, who are great amateur growers of Auriculas — 
a species of Primula — had long distinguished these two forms under the names 
“ pin-eyed ” and “ thrum-eyed ” respectively ; but Darwin first showed that we have 
here an adaptation for cross-pollination by means of insects — whatever part of the 
insect touches the anthers in one form coming in contact with the stigma in the other 
— which is not only structural. If pollen-grains from the two forms lie side by side 
on the stigma of either, those from the anthers of the form differing in length of style 
from the pollinated flower will be “ prepotent,” i.e. will be the first to germinate 
and so fertilise the ovules. Cross-pollination is thus physiologically safeguarded. 
