POLYPHONY 



6238 



POLYTECHNIC 



Polyphony (Gr. polys, many ; 

 phone, sound). Style of music in 

 which the constituent voices or 

 instruments pursue their own in- 

 dividual courses and preserve a 

 distinct melodic interest. It thus 

 differs from the monodic or homo- 

 phonic style, in which most of the 

 parts are simply accoinpunhnental 

 to the principal melody. A fugue or 

 a canon is necessarily polyphonic ; 

 other forms of music may or may 

 not be so, according to the desire of 

 the composer. See Harmony; Music. 



Polypodiaceae. An extensive 

 natural order of Pteridophytes. 

 It includes the greater number of 

 fern-genera, and is of world-wide 

 representation. With few excep- 

 tions they are perennial herbs 

 with leaves or fronds of a tough 

 texture, simple, or more or less 

 divided. The spores are borne in 

 minute stalked capsules, partially 

 girt by a vertical ring. These are 

 clustered in dots or lines on the 

 back of the frond. The frond be- 

 fore expansion is rolled up with 

 the tip in the centre of the coil. 



Polypody (Polypodium vulgar e). 

 Fern of the natural order Polypo- 

 diaceae. A native of Europe and 

 the N. temperate zone, it has a 

 fleshy rootstock, with a furry coat 

 of pale brown lance-shaped scales, 

 which creeps on the surface of tree- 

 trunks, walls, and hedge-bottoms. 

 The leathery fronds are cut into 

 lobes from the sides, and their 

 stalks are jointed to the rootstock 

 in such a way that they can be 

 thrown off when old. They are 

 produced singly at short intervals 

 along the rootstock, and remain 

 fresh and green throughout the 

 winter. The golden -orange clusters 

 of spore-cases are produced in 

 double rows on the back of the 

 lobes. The rootstock was formerly 

 employed as a purgative and for 

 whooping cough. See Fern. 



Pplyporus. Large genus of 

 fungi of the natural order Hy- 

 menomyceteae. It has spores 

 borne in minute tubes which are 

 sunk into the underside of the cap 



tached by a stalk to the surface 

 from which it grows. It consists of 

 fibrous tissue covered with epithe- 

 lium, and is inflammatory in 

 origin. Polypi are most frequently 

 met with in the nose, bladder, 

 rectum, or uterus. They rarely 

 become malignant, i.e. cancerous 

 in nature. If the growth is acces- 

 sible, it is as a rule easily removed. 

 Polytechnic (Gr. polys, many; 

 lechne, art). Term applied to any 

 institution affording practical train- 

 ing in the arts and sciences. Such 

 institutions are known also as 

 technical high schools. The term 

 was first used in connexion with 

 the Ecole Ccntrale des Travaux 

 Publics, established in Paris by 

 the National Convention in 1794, 

 and known since Sept., 1795, as 

 L'Ecole Polytechnique. Frequently 

 reorganized, it has been ever since 

 devoted to engineering. The first 

 London polytechnic, the Royal 

 Polytechnic Institution, 309, Re- 

 gent Street, and 5, Cavendish 



Polytechnic Institute at Battersea, London, opened Feb. 24, 1894, on 

 the site of the old Albeit Palace. Top, Regent Street Polytechnic 



Poly pores. Dryad's Saddle, P. squam- 



osus, a bracket-shaped species on a 



tree- trunk 



or pileus. The substance of the 

 pileus is corky or woody. They 

 mostly grow upon living or dead 

 wood trunks, branches, or roots 

 of standing trees or worked wood. 

 Those that grow from the trunks 

 usually take the form of brackets. 

 These are only one phase of the 

 plant's growth. The vegetative 

 phase takes the form of delicate 

 threads (mycelium) permeating 

 the tissues of "the wood and de- 

 stroying them. Many of the 

 species are highly destructive to 

 growing timber. See Forestry. 



Polypterus. Genus of mud- 

 fishes, found in the rivers of Africa. 

 The dorsal fin is broken up into a 

 series of small finlets arranged in a 

 row along the back, and the body 

 is covered with 

 large plate-like 

 scales. It grows 

 to a length of 

 about four ft., is 

 carnivorous in diet 

 and nocturnal in 

 habit. See Fish. 



Polypus. Tumour growing 

 from mucous membrane, usually 

 more or less pear-shaped, and at- 



Square, opened Aug. 6, 1839, was 

 devoted to the exhibition of new 

 inventions and lectures, a popular 

 feature being a diving-bell. In 

 1881 the premises became the home 

 of the Polytechnic Young Men's 

 Christian Institute, founded by 

 Quintin Hogg (q.v. ). Now known 

 as the Regent Street Polytechnic, 

 its educational courses and equip- 

 ment receive material aid from 

 the technical education board of 

 the L.C.C. and the city parochial 

 charities. 



The work carried on by means of 

 day as well as evening classes at 

 these polytechnics embraces both 

 theoretical and practical training 

 in class-rooms and laboratories, 

 while at most of them is a depart- 



Polypterus. the African mud-fish, showing dorsal fin 

 broken into small flnlets 

 ment for the teaching of domestic 

 economy to girls and women. 

 Similar institutions exist in other 



