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purple or white flowers. The relationship 

 of the genus is with Epidendrum, but the 

 lip is free, not connate with the column. 

 The sepals and petals are free, nearly equal, 

 and connivent ; the column semiterete 

 with two or three horns, and the anthers 

 four-celled, with four pollen-masses, each 

 with a recurved caudicle. [A. A. B.] 



ISOETES. A genus of Lycopodiacew, 

 with subulate fronds, a globose rhizome, 

 the apex of which is sunk, so that the 

 bases of the older leaves are higher than 

 those of the younger. The axillary capsules 

 are incorporated with the base of the 

 leaves, producing either antheridia in the 

 shape of small oblong spores, or larger 

 four-sided spores, which germinate by cell- 

 division of the apex in which archegonia 

 are formed, from whence ultimately the 

 new plant is produced. Most of the spe- 

 cies are strictly aquatic, but I. Hvstrix.* 

 which has lately been found in the Channel 

 Islands, grows in sandy places. The rhi- 

 zome is often rough, with dark horny 

 processes which are supposed to be abor- 

 tive leaves, to which the name of phyllo- 

 pods has been given. The leaves are stud- 

 ded with stomates, and the rhizome and 

 roots contain annular vessels like those of 

 JSquisetum. The genus occurs in all the 

 four quarters of the globe. [M. J. B.] 



ISOETOPSIS. The generic name of an 

 annual plant of the composite family found 

 in South and "West Australia. It gets this 

 name from the great outward resemblance 

 it bears to our common Isoetes. It has 

 numerous small sessile flower-heads, aris- 

 ing from the crown of the plant, and 

 surrounded by a few grassy leaves, whence 

 the specific name graminifolia. [A. A. B.] 



ISOGYRUS. Forming a complete spire. 



ISOLEPIS. A genus of cyperaceous 

 plants, belonging to the tribe Scirpece. 

 Distinguished by the inflorescence being 

 in spikes, two or three together or solitary ; 

 scales imbricated on all sides, all fiorife- 

 rous, or more rarely the exterior scales 

 empty ; stamens three, rarely fewer ; styles 

 three. Steudel describes two hundred 

 species, mostly natives of the warm tem- 

 perate zones of both hemispheres. The 

 British representatives are only two spe- 

 cies, namely 7. setaceus, and J. Savii, which 

 with most British authors simply form 

 a section of Scirpus. [D. M.] 



ISOLOMA. Lindscea. 



ISOMERIS. The name of a Californian 

 shrub, forming a genus of Capparidacece. 

 The flowers are yellow, with four equal 

 sessile petals ; stamens six, upon a fleshy 

 receptacle which is prolonged into a nar- 

 row appendage ; ovary stalked ; capsule 

 large, terminated by the short style. The 

 plant has a disagreeable odour. [M. T. M.J 



* The sculpture of the small spores or anthe- 

 ridia is not, however, precisely the same, but 

 more like that of /. Duriai, in the only specimen 

 we have seen. It may possibly, therefore, be a 

 species distinct from either. 



ISOMEROUS. Equal in number; an 

 isomerous flower is one all whose parts 

 are equal to each other in number. 



ISONANDRA. The inspissated milky 

 juice of one of the species of this genus of 

 Sapotacem constitutes the well-known Gutta 

 Percha, and ten other species are known. 

 They are all inhabitants of Southern India, 

 Ceylon, Malaya, and the adjacent islands, 

 forming lofty forest trees. The leaves are 

 entire and leathery. The flowers small 

 and inconspicuous, produced in little clus- 

 ters, either in the angles of the leaves or 

 at the ends of the young branches. They 

 have a four or six-parted calyx and co- 

 rolla enclosing double as many stamens, 

 which are all fertile. The ovary has four 

 or six cells, and eventually becomes a 

 fleshy fruit containing one or two oily 

 seeds. 



I. Gutta, the species which yields Gutta 

 Percha, is a large forest tree growing sixty 

 or seventy feet high, with a trunk two or 

 three feet in diameter. Its leaves are 

 inversely egg-shaped and entire, of a pale 

 green on the upper side, but covered be- 

 neath with short reddish-brown shining 

 down. The flowers grow in clusters of 

 three or more in the axils of the leaves. 



The Gutta Percha (or Gutta Taban) tree, 

 and its now famous product, was first 

 brought into notice about twenty years 

 ago by Dr. Montgomery at Singapore, 



Isonandra Gutta. 

 where the tree was then common, but the 

 Malays having adopted the extravagant 

 method of felling the trees in order to 

 obtain the milky juice, it is now quite ex- 

 tinct in that island, though it fortunately 

 exists in Borneo, Sumatra, and other east- 

 ern islands. The average quantity yielded 

 by each tree is 20 lbs. ; and as 18,593 cwt. 

 were imported into this country in 1859, 

 it follows that 104,120 trees would have to 

 be sacrificed for the supply of the English 

 market alone. The raw Gutta Percha ar- 

 rives in this country in lumps weighing 

 from five to six pounds, which are cut 

 into slices, softened in hot water, then 

 torn into shreds by rapidly revolving cy- 

 linders set with sharp teeth, and thrown 



