[Illustration: FIG. 61.--COMMON BILBERRY (_Vaccinium tenellum_).]
The plants comprised in this tribe, which is considered a separate order by many botanists, all agree with the genus Vaccinium in having the ovary entirely surrounded by the calyx, which forms a fleshy berry-like fruit when ripe, and in the seeds being scaly. _Vaccinium Myrtillus_, the common Bilberry or Blaeberry, is a familiar example of the genus; and _fig._ 61 shows the shape of the flowers at _a_, the manner in which the ovary is enveloped in the calyx at _b_, and the curious shape of the anthers in the magnified representation of them at _c_. The berry is five-celled and many-seeded; and there are eight or ten stamens. Both the anthers and the flower vary in the different species, but the calyx and the manner in which it surrounds the ovary are nearly the same in all, as may be seen in _fig._ 62, which represents a specimen of _V. tenellum_, the Pennsylvanian Whortle-berry. In this figure _a_ is the flower, _b_ the anther, and _c_ the ovary surrounded by the calyx.
[Illustration: FIG. 62.--AMERICAN WHORTLE-BERRY (_Vaccinium pennsylvanicum_).]
There are many species, among which may be mentioned the American Bluets (_V. angustifolium_); Deerberries (_V. stamineum_); Bluetangles (_V. frondosum_); the Hungarian Whortle-berry (_V. Arctostaphylos_); and the Cow-berry, or common British Whortle-berry (_V. Vitis-Idæa_).
The Cranberry (_Oxycoccus palustris_) differs from the genus Vaccinium in the shape of its flowers (see _fig._ 63), and in its anthers being without spurs; there are eight stamens, the filaments of which are connivent, that is, growing close together. The American Cranberry (_O. macrocarpus_) differs from the European kind, principally in having larger fruit.
This tribe is also considered as a separate order by many botanists; but the principal distinction is the long arillus or skin which enfolds the seeds and gives them the appearance of being winged. The most remarkable genera are _Pyrola_, the Winter Green, of which there are several species common in moist woods in the north of England and Scotland; and _Monotropa_, or Bird's-nest, parasitic plants which grow on the roots of pine and beech-trees, but are by no means common in England. The species of Pyrola are pretty little evergreen plants, with white flowers, the corollas consisting of five distinct petals, and which have ten stamens, the anthers of which are two-celled, each opening by a pore; the style is single, ending in a capitate stigma cut into five lobes; and the capsule is five-celled. The yellow Bird's-nest, (_Monotropa Hypopitys_) has a coloured stem, with drooping flowers, and numerous scales instead of leaves, of which it is destitute. The flowers have a coloured calyx cut into four or five segments, and the corolla is in four or five petals. There is an American species with white flowers.