A similar embarrassment takes place when the calyx, in its metamorphosis, inclines too visibly in the direction of the corolla. Thus, in the _Polygala vulgaris_,--a little, vivacious, and very abundant plant,--the two inner leaflets of the calyx are not only larger than the three other outer leaves, but they are coloured like the petals, and become, towards the close of their flowering time, membranous, herbaceous, and marked with three strong veins: they resemble the wings of a butterfly, and have been called wings.
These peculiarities are useful in the distinction of certain species, which, at bottom, are simply varieties. Thus, in the _Polygala Austriaca_ (_Polygala amara_ of Keoch, _Polygala uliginosa_ of Reichenbach),--a plant with small white or bluish leaves, which is sometimes met with on the borders of peaty swamps,--the central vein or ridge of the wings is simple, and never anastomoses with the lateral veins; while, in the _Polygala vulgaris_, as well as in the _Polygala depressa_ and _Polygala amarella_, the vein is ramified, and anastomoses more or less widely with the laterals.
But since we are upon this subject, why should we not seize the opportunity of familiarising ourselves, under the form of a digression, with the little family of the Polygalaceæ? But no; we will adjourn the episode, since it would cut the thread of our discourse upon the calyx, our _calicology_.
Some calices there are, which, by their colouring, approximate so closely to the second floral envelope, that one is always tempted to call them corollas.
The yellow calyx of the furze (_Ulex Europæus_), and of a kind of hellebore (_Helleborus hyemalis_);
The rosy calyx of the Christmas rose (_Helleborus niger_);
The blue calyx of the larkspur (_Delphinium Ajacis_); and the Napel aconite (_Aconitum Napellus_).
In the _Aquilegia vulgaris_, and in the _Trollius Europæus_, the calyx, by the form and colouring of its leaflets, is confounded with the second whorl so completely, that Linnæus gave it the name of _corolla_.
Nevertheless, in the midst of these waverings, which lead us to mistake the calicinal leaflets sometimes for bracts, sometimes for petals, we recognise perfectly the foliaceous type. Independently of its colour, which is generally green, the calyx has the same organisation as the leaf; we find in it the same tracheæ and the same stomata, the same glands and the same hairs; the veins and ramifications are also the same; and, in more than one instance, the calicinal leaflet resumes the character of a veritable leaf. Look, for example, at the five leaflets, united so strongly at the base but so free at the top, arranged in the form of a quincunx, of the hundred-leaved rose. The two external, enlarged, and lanceolate pieces are garnished on the right and left, and often at the point, with tiny foliaceous appendages, which, in every respect, imitate the composite leaf that carries the slender stem. And if we move aside the external or bearded parts of the calyx, we see that the internal bear less and less resemblance to a leaf. Thus, the part which comes next is _semi-bearded_; that is to say, it is furnished with foliaceous appendages only on one side; and the two upper pieces are _beardless_, that is, reduced to the dilated central vein.