486 



POLLICIPEDE POLYOMMATUS. 



It is a peculiarity in the nests of the European 

 Polistes that the cells are not arranged horizontally, but 

 vertically, which is probably owing to the circumstance, 

 that, as there is no outward covering to the nest, 

 the rain would lodge in the cells if they were placed 

 in an upright position, whereas, when arranged ver- 

 tically, the rain falls off without resting. The fol- 

 lowing is a figure of the nest of Polistes Gallica, a 

 species somewhat smaller than the common wasp, 

 and of the same colours, and which is interesting on 

 account of its being the species attacked by the Xenos 

 Rossii of Kirby. 



Some of the species having the second joint of the 

 abdomen very large, the preceding forming a clavate 

 peduncle, have been separated into the genus Epipone. 

 The Vespatatua and nidulans of Fabricius belong to this 

 genus, the latter of which with its nest and parasite, be- 

 longing to the genus Chalets, is figured by Reaumur in 

 the sixth volume of his Memoirs. The nests of these 

 species are very large, and are suspended in trees, the 

 exterior of the nest being composed of the most beau- 

 tiful paper-like material, over which from its fine 

 polish the rain glides without doing the least damage. 

 The study of the exotic species of these genera re- 

 quires much attention, and has hitherto been greatly 

 neglected. 



POLLICIPEDE (Leach). A genus of molluscs, 

 constituted by the late Dr. Leach, but now considered 

 only a species of the genus Pentalepcts. 



POLYERGUS (Latreille). A genus of ants. 

 See FOBMICID.S. 



POLYGALA (Tournefort). A genus of hand- 

 some evergreen shvubs, all from the south of Africa, 

 of perennial herbs, natives of Europe, and a good 

 many annuals from North America. The flowers are 

 diadelphous, and the genus belongs to the order to 

 which it gives a title, viz. 



POLYGALACEJG. A natural order of plants, 

 consisting of six genera and sixty -four species. The 

 genera are Polygala, Muraltia, Mundia, Securidaca, 

 Krameria, and Monina. Most of this order are inte- 

 resting to the lover of plants, as well for the neatness 

 of their foliage as for their handsome flowers. The 

 PolygaletE are remarkable for the union of their stamens 

 into a single body, their one-celled anthers opening 

 with a pore and their irregular petals, one of which 

 is often keel-shaped, and beautifully bearded. The 

 leaves have generally a bitter astringent taste, and 

 the European species are stomachic and stimulant, 

 and are supposed to possess an influence over the 

 lacteal secretion of cattle fed upon them ; hence they 

 have received the name of milkwort. Several of 



them are useful medicines ; while one, th P. vene~ 

 nata, a native of Java, is remarkable for the poisonous 

 qualities attributed to its leaves, which, if onl y touched, 

 produce violent sneezing and oppressive faintness. 

 Monina polt/stachya, is the yal-hoe of Peru, where it 

 is used as a cure for dysentery. Krameria deviates 

 more than any other genus in this very natural group 

 from the normal structure of its associates ; its sepals 

 are generally four, rarely five ; the stamens four or 

 three, and single, or but slightly connate by their 

 filaments. K. triandra is the rhatany, which is a 

 valuable astringent tonic. The whole are propagated 

 by cuttings or seeds. 



POLYGONACEjE. A natural order comprising 

 fourteen genera and above one hundred and eighty- 

 eight species. The knot-wort, the rhubarb, the sorrel 

 and the dock, which, with other associated genera, 

 form this type, are herbaceous, rarely shrubby plants 

 or trees, with knotted stems and branches, simple 

 alternate leaves, revolute in vernation, dilated sheath- 

 ing petioles, and acreate stipules. The flowers are 

 in general united, sometimes separated, and either 

 solitary or disposed in fasicles or racemes. The 

 perianth is free, regular, persistent, without sepals, 

 often coloured with a three to six parted limb. The 

 stamens are definite, exserted from a torus, lining 

 the bottom of the calyx ; the filaments are free, the 

 anthers two-celled, opening lengthwise ; the germen 

 is superior, one-celled, and contains a solitary ovule ; 

 the styles are from two to three, and the stigmas simple 

 or feathery. The fruit is dry and indehiscent, bladder 

 or nut-like, and often covered by the persistent calyx. 



Along with many of the most common weeds which 

 cover waste ground in every latitude, there will be 

 found in this type several important officinal and 

 dietetic plants, the chief of which are the rhubarbs, 

 the sorrel, and the buck-wheat. 



The genera in this order are Coccoloba, Polygonum, 

 Oxyria, Snmnichia, Tragopyrum, Atraplia.rts, Kumex, 

 Etnex, Podojrtenis, Triplarin. Rheum, Citlligmnnn, 

 Eriogonum, and A'amigia. 



POLYLEPAS (Cuvier). A genus of molluscs, 

 belonging to the family Lepidacea, one species of 

 which constitutes Dr. Leach's genus Scalpellnm. 



POLYOMMATUS (Latreille). A genus of but- 

 terflies, comprising the pretty little blue species so 

 common in our fields, and belonging to the family 

 LYC^ENID^E (which see). This is a very extensive 

 genus, distinguished by having the posterior wings 

 destitute of a tail or produced anal angle. The 

 British species are termed blues, from the elesrant 

 shades of that colour with which the upper side of 

 the wings are ornamented, whilst the beautiful eye- 

 like spots on the under side of the winars have given 

 rise to the generic name, which is derived from the 

 Greek, and signifies " many eyed." The larva 1 feed 

 upon various kinds of grasses. These pretty little 

 butterflies are amongst the objects which do not fail to- 

 attract the attention of the most incurious in a sum- 

 mer day's stroll. " We have few more jealous and 

 pugnacious insects," says Mr. Knapp, " than the little 

 elegant blue argus butterfly (P. alexis, Stephens), 

 noted and admired by all. When fully animated, 

 it will not suffer any of its tribe to cross its path, 

 or approach the flower on which it sits, with im- 

 punity ; even the large admirable (Vanessa atalanta') 

 at these times it will assail and drive away. There 

 is another small butterfly, the copper (Lyctena phlaas, 

 Fabricius), however, as handsome, and perhaps still 



