631 



Wfyt t£rea£urg at ISntang. 



[iSOT 



into cold water, -when the impurities sink 

 and the Gutta Percha floats on the surface. 



. The shreds are then transferred to hot 

 water, and are made into solid masses 



' which are afterwards kneaded by machi- 



! nery, in order to expel the extraneous 

 moisture. 



One of the first uses to which Gutta 

 Percha was applied in this country was 

 for the soles of boots, its imperviousness 



; to water and great durability recommend- 

 ing it for such purposes. From its pro- 



! perty of becoming plastic by heat, it. is 



! valuable for modelling and moulding, 

 and it is used for making a variety of 

 useful articles, such as door-handles, pipes, 

 plates, buckets, ear-trumpets, &c; but 

 its most important use is owing to its 

 being a non-conductor of electricity, which, 

 combined with its indestructibility in sea- 

 water, renders it applicable for coating 

 the wires employed for submarine tele- 

 graphs. Alkalies, vegetable acids, and 

 weak mineral acids, also, do not act in- 

 juriously upon it, but strong sulphuric, 



; nitric, and hydrochloric acids corrode it, 

 and turpentine, benzole, chloroform, &c, 

 completely dissolve it. [A. S.] 



ISOXEMA. A genus of dogbanes, hav- 

 j ing the corolla salver-shaped with a five- 

 parted border, its tube without scales ; 

 the filaments of the anthers simple at the 

 apex ; and the base of the ovary without 

 scales. I. Smeathmanni is the only species ; 

 it is a small hairy shrub, native of tropical 

 Africa, with opposite leaves, and terminal 

 clusters of flowers. [G. D.] 



ISOPAPPUS. A genus of composite 

 plants, found in Texas. The two known 

 species are hirsute annual herbs, with nu- 

 merous lance-shaped leaves, and an abun- 

 dance of small yellow-rayed flower-heads, 

 supported on slender stalks, and disposed | 

 in loose much-branched panicles. From 

 Stenotus, and other allies, they differ in the 

 narrow scales of the involucre, and in the ' 

 pappus being composed of a single series 

 of capillary nearly equal bristles : whence 

 the name. [A. A. B.] 



ISOPHOROUS. Transformable into 

 something else. Thus, Actinia is an iso- 

 phorous form of Dendrobium, Paxtonia of 

 Spathoglottis, and, according to Morren, 

 Anguloa and Lycaste of Maxillaria. 



ISOPHYSTS. A genus of Melanthacece, 

 also called Hewardia. It consists of a sin- 

 gle Tasmanian species, /. tasmanica, with 

 dry rigid, distichous, equitant, narrow, 

 sword-shaped leaves, and purple flowers on 

 bracteated scapes, taller than the leaves. 

 The perianth is six-leaved, spreading in a 

 star-like form, the segments acuminate ; 

 there are three stamens, with short broad- 

 ly subulate filaments; and a pyramidate, 

 bluntly three-cornered, three-celled, many- 

 seeded ovary, with a short style, and three 

 thick recurved stigmas. The spathes 

 which terminate the scapes are one or 

 two-flowered. [T. MJ 



ISOPLEXIS. A genus oiScrophulariaceos, 



consisting of two species, formerly in- 

 cluded under Digitalis, but distinguished 

 by Lindley on account of their shrubby 

 habit, and their corolla, of which the upper 

 lobes are reflexed. Both the I. Sceptrum, 

 from Madeira, and I. can ariensis, from the 

 Canary Islands, have been in cultivation 

 in our greenhouses ; they are handsome 

 plants, with terminal racemes of showy 

 yellow or orange-coloured flowers. 



ISOPOGON. An extensive genus of 

 Proteacece, forming large shrubs or small 

 trees, natives of the extra-tropical parts of 

 Australia, principally in the south-west 

 portions of it. The foliage is harsh and 

 rigid, the leaves being of various forms, 

 simple or much divided. They are filiform 

 and sharp-pointed in I. petrophiloides, I. 

 teretifolius. &c. ; lanceolate and leathery in 

 texture in /. attenuatus, I. longifolius, &c; 

 wedge-shaped and deeply toothed in I. tri- 

 partitus, I. Baxteri, &c. ; and broadly ovate 

 in /. latifolius. The flowers grow in glo- 

 bose, generally terminal heads, and have a 

 regularly four-cleft calyx bearing on each 

 of its concave segments a nearly sessile 

 anther, a filiform style with a cylindrical 

 or spindle-shaped stigma. The nut con- 

 tains a single wingless seed. [R. H.] 



ISOPTERYX. A genus of Begoniacew, 

 and the type of one of the sections of that 

 order, according to Klotszch. Its charac- 

 ters are : petals of staminate flowers, four, 

 ciliately toothed at the apex ; anther oval, 

 short ; filaments very long, not united ; 

 branches of the styles bipartitely multifld, 

 and papillose, with slender somewhat 

 terete lobes; fruit top-shaped, of a some- 

 what cartilaginous and papery consistence, 

 three-horned above, attenuated at the 

 base, shortly lengthened out at the apex. 

 The horns are short cuspidate erect in- 

 curved. The one species referred hither 

 is a native of New Grenada. [J. H. B.j 



ISOPYRUM. A genus of Ranunculacew, 

 with the habit of Thahctrum, but really 

 more nearly allied to Helleborus. They, 

 are natives of Europe and temperate Asia, 

 and are slender herbs, with the leaves 

 ternately divided, and with the leaflets 

 again ternate or three-lobed. The flowers 

 are stalked, without involucres, white, 

 with five rather large petaloid sepals, and 

 five or ten minute petals, tubular at the 

 base, two-lipped; stamens ten or more; 

 ovary of two to twenty carpels, which be- 

 come follicles, containing several seeds 

 each. I. thalictroides is not uncommon 

 in central and southern Europe. [J. T. S.J 



ISOS. In Greek compounds = equal. 

 Placed before the name of an organ, it in- 

 dicates that it is equal in number to that 

 of some other which is understood : thus, 

 isostemonous is said of plants the sta- 

 mens of which are equal in number to the 

 petals. 



ISOTOMA. A genus of lobeliaceous 

 herbs, distinguished principally by the 

 salver-shaped corolla, the segments of 

 which are spreading and nearly equal. 



