915 



Ct)c Crotfurg of 3S0tanp. 



[poly 



perianth is funnel-shaped or bell-shaped, 

 usually pink -white or red, five-cleft, the 

 segments somewhat unequal, persistent, 

 and usually increasing in size after flower- 

 ing , stamens five six or eight (very rarely 

 four or nine) ; styles two to three ; nut len- 

 ticular in the species with two, and three- 

 edged in those with three styles. Several 

 of the species are astringent, as Bistort, 

 P. Bistorta, which is occasionally used in 

 medicine ; others are acrid, as the Water- 

 pepper, P. Hydropiper ; and some fur- 

 nish a blue dye, as the Chinese P. Undo- 

 rium. The genus is divided into the 

 following sections:— Bistorta, the British 

 species of which are P. Bistorta and P. 

 viviparum; Amblygonum, of which the 

 garden Persicary, P. orientate, is a good 

 example ; Persicaria, represented by P. 

 amphibium, lapathifolium, laxum, Persica- 

 ria, mite, Hydropiper, and minus; Eciri- 

 nocaulon and Cephalophilon, both extra-Eu- 

 ropean ; Aconogmion, of which one species, 

 P. alpinum, occurs in Europe ; Tiniaria, 

 comprising the British P. Convolvulus and 

 dumetorum : and Aviculaiia, of which three 

 species occur in Britain, P. aviculare, 

 Eaii, and maritimum. [J. T. S.J 



P. Convolvulus, the Climbing Buckwheat, 

 is often a great weed-pest, as it twists 

 around the stems of the crop, and not only 

 strangles it, but keeps away sun and air 

 by reason of its large leaves. P aviculare, 

 the Knot-grass, and P. Persicaria and la- 

 pathifolium, Persicary, are three very 

 troublesome agrarian weeds, and more es- 

 pecially where manure is much employed. 

 These species, indeed, will always be 

 found growing on exposed dung-heaps, 

 where they seed freely, and from which 

 these- plants are doubtless for the most 

 part spread over our fields. P. Hydropiper, 

 the Biting Persicaria, derives its trivial 

 name from its acrid and biting taste. It 

 has been employed in medicine as a diuretic, 

 for which purpose the green herb is used, 

 as its properties are lost in drying. 



The Snakeweed, P. Bistorta, is a pretty 

 species which is not uncommon in old- 

 fashioned gardens, where it was probably 

 grown not only as a flower, but as a medi- 

 cine. It occurs frequently growing in iarge 

 circular patches in meadows, and espe- 

 cially those near villages, from which it 

 may be inferred that it has become natu- 

 ralised as a British plant. We are informed 

 by Mr. Robert Holland, that the green tops 

 are eaten in Cumberland under the name of 

 Easter Man Giants (.? Easter-eating— Fr. 

 mangeant). The roots were formerly much 

 used in medicine: as they are highly as- 

 tringent, their decoction in water is found 

 useful as an astringent injection, and as a 

 gargle in sore-throats. See also Fagopy- 

 BCM. [J. B.] 



POLYGYRIA. Having many distinct 

 styles. 



POLYIDES. A genus of rose-spored 

 Alga?, consisting of a single species which 

 is so like Furcellaria fastigiata that it is not 

 easy to distinguish it except when in fruit. 

 This forms a spongy mass composed of 



vertical articulate threads containing nu- 

 merous globose compound nuclei, the 

 spores of which are large and obconical and 

 radiate from a central point, and is so 

 singular that the genus is referred to a dis- 

 tinct natural order, Spongiocarpece. P. ro- 

 tundus, not uncommon on our coasts, oc- 

 curs also in the United States. [M. J.B.] 



POLYLEPIDOUS. Having many scales, j 



POLYMERIA. A small genus of East- I 

 ern Australian Convolvulace (^distinguished 

 from Convolvulus by its four to six acute 

 stigmas, and by having only one ovule in 

 each of the two ovary-cells. [A. S.] 



POLYMEROUS. Consisting of mam- 

 parts. 



POLYMNIA. A genus of Compositce of 

 the tribe Helianthece, consisting of erect 

 herbs with alternate or opposite leaves, 

 often large or deeply lobed, and termi- 

 nal corymbose flower-heads with a yellow 

 ray and usually a dark-purple disk. The 

 involucre has five outer spreading leafy 

 bracts and several inner smaller ones em- 

 bracing the achenes. The ray-florets are 

 female, producing obovate achenes without 

 any pappus ; the disk-florets all male with 

 linear abortive achenes. P. Uvedalia and P. 

 canadensis are common in some of the hilly 

 districts of Uorth America, and about half 

 a dozen more species are South American. 



POLYPETALOUS. Having the petals 

 perfectly distinct from each other. 



POLYPHORE. A receptacle which bears 

 many distinct carpels, as in Crowfoots. 



POLYPODE, or P. DE CHENE. (Fr.) 

 Polypodium vulgare. 



POLYPODIACE.E. A natural order of 

 ferns,comprising nearly all that are known, 

 the other orders, Marattiacece and Ophio- 

 glossacece, being of very limited extent. 

 The chief distinguishing feature consists 

 in the presence of an elastic jointed ring 

 nearly surrounding the spore-cases. By 

 this peculiarity they may at once be recog- 

 nised in all cases, except in the genera 

 Osmunda and Todea in which the ring is 

 always, and in Ceratopteris in which it is 

 sometimes, more rudimentary. In all these 

 cases, however, the ring is present ; and 

 hence the Polypodiacece are called annu- 

 late ferns, while the Marattiacece and Ophio- 

 glossacece, in which the ring is absolutely 

 wanting, are called exannulate. See Fili- 

 CES. [T. M .] 



POLYPODIUM. The typical genus of 

 the Polypodiece, and known at once by hav- 

 ing its fronds plane not indusiiform at the 

 edge, its veins free, and its son globose and 

 naked. It is an extensive genus, of the 

 most varied aspect, and distributed all 

 over the world, presenting itself in some 

 half-dozen distinctive forms : as, for ex- 

 ample, with terminal sori and articulated 

 fronds, as in P. vulgare ; with terminal sori 

 and articulated fronds and pinnas, as in P. 

 tenellum; with terminal sori on obovate 

 receptacles and adherent fronds, as in 



