POL 



678 



POL 



having pistils and stamina, and producing 

 one seed. 



POLYGA'MIA FRUSTRA'NEA. An order of 

 the class Syngenesia, of the sexual system 

 of plants. Florets of the disk perfect ; 

 those of the circumference with an abor- 

 tive pistil, or it is wanting altogether. 



POLYGA'MIA NECESSARIA. An order of 

 the class Syngenesia , of the sexual system 

 of plants. Florets of the disk with stamens 

 only ; those of the radius with pistils only. 



POLYGA'MIA SEOREOA'TA. An order of 

 the class Syngenesia, in the sexual system 

 of plants. Plants with several flowers 

 either simple or compound, but with 

 united anthers and a proper calyx, all in- 

 cluded in one common calyx. 



POLYOA'MIA SITPERFLUA. An order of 

 the class Syngenesia, of the sexual system 

 of plants. Florets of the disk of the com- 

 pound flowers perfect : those of the cir- 

 cumference having pistils only ; but both 

 kinds producing perfect seed. 



POLYG'ONVM. Persicaria or Knot-grass. 

 An extensive genus of holoraceous plants. 

 Octnndria Trigynia. Name from 3-0X115, 

 many, and yew, a joint. There are at 

 least ten indigenous species of polygonum, 

 among which are the Bistort, or Snake- 

 weed, Water-pepper, Common Knot- 

 grass, Buck- wheat, and Black Bird- weed. 



POL'IGLOTT, from sroXfs, many, and 

 yX*iTT, tongue. 1. Having many lan- 

 guages. 2. A hook, particularly the 



Bible containing the Scriptures in several 

 languages. 



POL'YGON, from troXus, many, and 

 yavia, an angle. 1. A geometrical figure 

 of many sides and angles. 2. In forti- 

 fication, an exterior polygon is the distance 

 of one point of a bastion from the point 

 of another, reckoning all round the works : 

 an interior polygon is the distance between 

 the centres of the bastions, reckoning 



round as before. 3. In mechanics, when 



a series of more than three forces act in 

 equilibrium upon one point, they may be 

 represented in direction and intensity by 

 a polygonal figure ; this figure is termed 

 the polygon of those forces. 



POLYG'ONAL KCMBERS. The successive 

 gums of a series of numbers in arith- 

 metical progression. 



POLTGAS'TRICA. An order of animal- 

 cules especially characterised by numer- 

 ous cavities or stomachs (sometimes up- 

 wards of 200) : whence the name tro^us, 

 many, and ycttrrv^, a stomach. Almost 

 all the known genera of polygastric ani- 

 malcules possess eyes : they are also 

 found to possess an acute sense of taste ; 

 distinguish, pursue, and seize their prey; 

 and although so excessively minute that 

 t.ono.OOO have been calculated as being 

 obtained in one drop of water, tLey 



avoid infringing upon each other when 

 swimming. There is no proper skeleton, 

 nor any secretion of shell ; yet there are 

 parts destined to give support. In the 

 majority there is an alimentary canal, 

 but no teeth for mastication. Notwith- 

 standing their extreme minuteness, they 

 appear to be the most numerous, the 

 most prolific, the most active, and the 

 most voracious of all living beings. 



POL'TGKAM, ?roXws and yqctu.ua, line. 

 A figure consisting of many lines. 



POL'YGRAPH, from jreXus, many, and 

 ^gato> to write. An instrument for 

 multiplying copies of a writing. 



POLYGYN'IA, from rcXi/s, many, and 

 yuvY, , a female. An order of plants having 

 many pistils. 



POLY'HALLITE, from araXy?, many, 

 aAs, salt, and X<0os, stone. A mineral 

 which occurs in masses of a fibrous tex- 

 ture at Ischel, in Austria, and is thus 

 named from its containing sulphates of 

 lime, magnesia, potash, and soda, coloured 

 red by peroxide of iron. Lustre pearly. 



POLYHE'DRON, from 5reAi/s, many, and 

 ib, a side. 1. A solid contained under 



many sides or faces. 2. A multiplying 



glass: a lens cut into many facets/dis- 

 posed in a convex form. 



POLYMIG'NITE, from a-cAws, many, and 

 [M-ywfju, to mix. A recently discovered 

 mineral, so named in consequence of the 

 variety of its constituents : titanic acid, 

 zirconia, lime, yttria, oxides of iron, ceri- 

 um, and manganese, with minute por- 

 tions of magnesia, potash, silica, and 

 oxide of tin. It is of a black colour, and 

 metallic lustre ; crystallised in small 

 prisms. Sp. gr. 4'8. 



POLTM'NITE. A stone, so named from 

 3-oXws and ^05, because it is marked with 

 dendritcs and black lines, so disposed as 

 to represent rivers, marshes, and ponds. 



POI/YMORPHS, from sroXus, many, and 

 fMf$vi, form. Small and irregular shells 

 not referred to any known genera. 



POLYNO'MIAL, from jreXws, many, and 

 ovofAct, a name. An algebraical name for 

 any quantity consisting of several terms, 

 as, ax + bx 2 + ex 3 dx 4 . 



POL'TPARIA. See POLYPI. 



POL'TPE, 1 IleXr/jrou?, from v;, 



POLT'PUS. / many, and vcus, a fo>t. 1. 

 Something that has many feet or roots. 

 The name has been used to designate a 

 peculiar description of tumour which 

 grows in the nose, from the erroneous 

 idea that it has usually several roots or 



feet. 2. The name Polype has been 



used to designate the individual tubes, 

 with their tentacula, of the Polypu$, re- 

 serving this last as the name of the &f 



