285 



1LMENITE. 



INDIA-RUBBER. 



228 



ILMENITE. [TITANIUM.] 



ILUANTHUS. [ACTINIAD*.] 



ILVAITE, a native Silicate of Iron, identical with Yenite. [IRON.] 



IMBER. [COLYMBID*.] 



IMBRICARIA. [SAPOTACE*.] 



IMPATIENS, a genus of Planta so called from the sudden and 

 elastic force with which they burst their capsules ; hence ' Noli me 

 tangere ' is the name of one of the species. Another is well known as 

 a highly ornamental annual by the name of Balsam, whence the natural 

 family to which it belongs has been called Balsaminaceae. [BALSAMIN- 

 ACE.E.] The genus is especially an East Indian one, though single 

 species extend into Europe, Siberia, and North America. Liunseus 

 was only acquainted with 7 or 8 species; but Dr. Wight, in the 

 ' Madras Journal,' vol. ii., states that not less than 100 species are now 

 known, and almost entirely from the mountains of the peninsula of 

 India and the Himalayas; in those from Silhet as far north as the 

 Sutlej, and in 30 N. lat., at as great elevations as 7000 feet. They 

 are absent from the plains of India ; some are found on the Malabar 

 coast, little elevated above the sea, but only during the monsoon. 

 Dr. Itoyle has stated that they are only found in the Himalayas during 

 the rains, and hence inferred that the moisture and moderate tempera- 

 ture, as well as the equability of both during the rainy season, is as 

 favourable to their growth as the heat and moisture of the peninsula ; 

 . Wight has since ascertained that the species are chiefly found 

 at elevations of 4000 and 4500 feet, in a season where there is moisture 

 combined with a moderate but equal temperature. These facts are 

 important as showing the influence of climate on vegetation ; and 

 useful as affording hints and principles for the cultivation of these 

 plants at a lower temperature than is necessary for the plants of the 

 plains from the same latitudes, though great success has been attained 

 in the cultivation of Balsams in this country. 



IMPERATO'RIA (so named from its supposed imperial virtues in 

 medicine), a genus of Plants belonging to the natural order UmbeUifera;. 

 It has no calyx ; obovate petals, contracted into an indexed segment ; 

 the fruit flattened at the back, with a dilated flat border. The species 

 are glabrous perennial herbs, with erect hollow terete striated stems. 

 The umbels are large and compound, and the flowers white. 



/. OstrutMum has a tuberous fleshy and somewhat creeping root of 

 an aromatic and acrid nature ; the lower leaves biternate, the upper 

 ones less compound ; the flowers are small, and of a white or pale 

 flesh-coloured hue. It is a native of Europe and Newfoundland in 

 damp meadows and woods. This species is the Masterwort of old 

 English herbalists, and the root has been much celebrated as au 

 antidote against poisons, a diuretic, and sudorific ; and Lerango 

 affirms that an infusion of it in wine has cured agues which have 

 resisted quinine. When chewed it excites a copious flow of saliva, 

 and acts as an agreeable stimulant to the gums. It is recommended 

 in cases of rheumatic toothache, and is cultivated in many places for 

 the London market. 



/. anjtutifuUa, the Narrow-Leaved Masterwort, has biternate leaves, 

 oblong leaflets, attenuated at the base and deeply serrated. It is a 

 native of the Alps and Piedmont. The blossoms appear in June and 

 July, and are of a white colour. The species of this genus are of 

 easy culture, and may be propagated either by dividing the roots or 

 from seed. 



(Don, DiMamydeota Planti ; Lindley, Flora, Medico, ; Burnett, 

 it/ Una of Botany.) 



IMPEYAN. [PHASIANID*.] 



IMPREGNATION. [REPRODUCTION IN PLANTS; REPRODUCTION 

 is ANIMALS ; STAMEN ; PISTIL.] 



I'NACHUS, a genus of Brachyurous Crustaceans, placed by M. 

 Milne-Edwards under his tribe Macropodians. [MACBOPODIANS.J 



INCISORS. [DENTITION; TEETH.] 



INCUS. [EAR.] 



INDIA-RUBBER, the common name of a vegetable compound 

 which is found in all plants with a milky juice. It is alao known by 

 the name of Caoutchouc. 



The existence of a milky juice in many plants, which flows from 

 them when their tissues are wounded, is a fact that has been familiarly 

 known from time immemorial. It is however only a matter of recent 

 discovery that this milky juice characterises certain families of plants. 

 Although the great majority of plants which yield this juice in abund- 

 ance are tropical, yet they are not without their European repre- 

 sentatives. The Spurges, Dandelion, and Celandine of our road-sides 

 are instances. The families of plants which furnish this milky juice 

 in the greatest abundance are Muracece, Euphorbiaceai, Artocarpacece, 

 Apocynacta, Cichoraceoe, Papaveraceie, Ca,mpanv,lacece,&uALnbdiacete. 



This juice, which is called by botanists ' the milky juice,' because 

 it has an appearance similar to milk, has also the physical constitution 

 of that fluid. It is an aqueous liquid, charged with soluble matter, 

 in which float globules of a substance insoluble in water, and which 

 are by their tenuity held in suspension in the liquid, but for which 

 they have no affinity, in the same manner as butter is held in sus- 

 pension by milk. From the difference of the refractive powers of 

 these two substances, each of which taken separately would be colour- 

 less or transparent, arise the opacity and white colour of the two : 

 hence the compound is properly called a ' milky juice.' 



The analogies which this juice exhibits with the milk of animals and 

 HAT. HIST. D1V. VOL. III. 



vegetable emulsions are seen in the manner in which it acts when left 

 to itself. Run out into the air, received aud preserved in close vessels, 

 it separates itself into two layers, as milk itself would do. The watery 

 part very soon has an insoluble part floating upon it, which collects 

 together and swims at the top as cream swims upon milk, and which 

 forms nearly the half of the entire mass. But with these physical 

 resemblances the analogies cease. That which in milk and in emul- 

 sions produced from seeds collects on the surface of the aqueous 

 liquor is, properly speaking, a fatty body, containing oxygen in its 

 composition ; while the kind of cream which swims upon the milky 

 juice is a compound of carbon and hydrogen. 



This substance has long been known to the natives of both the Old 

 and New World, in Hindustan and South America. It was not how- 

 ever till the expedition of the French academicians to South America 

 in 1735 that its properties and nature were made known in Europe 

 by a memoir upon it by M. de la Condaminp. This notice excited 

 little attention ; and subsequently notices of this substance were sent 

 to the French Academy in 1751 by M. Fresnau, and in 1768 by 

 M. Macquer. At the latter end of the last century and the beginning 

 of the present it was brought into this country in small quantities, 

 where, on account of its being used for rubbing out black-lead pencil 

 marks, it acquired the name of India-Rubber. 



Although after its application to the water-proofing of garments its 

 consumption gradually increased, the importation into the United 

 Kingdom in 1830 appears not to have been more than 50,000 Ibs. 

 In 1842 the import of this article had increased to between 700,000 

 and 800,000 Ibs. Up to the present time the consumption of India- 

 Rubber has prodigiously increased; and one port alone in South 

 America is said now to send to Great Britain nearly 4000 cwts. 

 annually. To the large consumption in the United Kingdom must 

 be added that of America, where the application of Caoutchouc has 

 been much more general and successful than even in our own country. 



The particular species of plants which are employed for procuring 

 India-Rubber are very numerous, and it is probable that many yield 

 it which are not yet known to botanists. The tree which supplies 

 most in Continental India is the Ficui elastica, a tree belonging to 

 the order Moracece ; it is exceedingly abundant in Asam. All the 

 species of Fictu yield Caoutchouc to a greater or less extent in their 

 juices, and even the Common Fig (Pints Carica) of Europe contains it. 

 Species of Ficu produce the Caoutchouc brought from Java; aud 

 F. radula, P. ettiptica, and F. prinoides are amongst those mentioned 

 as affording a portion of that brought from America. Next to the 

 Muracece the order Euphorbiaceai yields the largest quantity of 

 Caoutchouc. The Siphonia elastica, a plant found in Guyana, Brazil, 

 and extending over a large district of Central America, yields the 

 best kinds of India-Rubber that are brought into the markets of Europe 

 and America. To another order, Apocynaceie, we are indebted for 

 the Caoutchouc which is brought from the islands of the Indian 

 Archipelago. The plant which is the source of this substance in those 

 districts is the Urceola elastica, a climbing plant of very rapid growth 

 and gigantic dimensions. A single tree is said to yield, by tapping, 

 from 50 to 60 Ibs. annually. Many other plants of this order yield 

 Caoutchouc, and of those given on good authority we may mention 

 CoUophora utila aud Cameraria latifolia, plants of South America ; 

 Vahea, gummifera, in Madagascar ; and Willurjltbeia edidis, in the Kast 

 Indies. To this order belongs the Cow-Tree, or Hya-Hya (Tahernas- 

 iii 'i a i n a 1 1 ni His), of Tropical America, which yields a milky juice that 

 is drunk by the natives of the district in which it grows. 



The Caoutchouc, whilst it is in the tissues of the plant, is evidently 

 in a fluid condition ; but after its separation from the other fluid parts 

 its consistence becomes changed, and it forms a solid mass similar in 

 its external characters to vegetable albumen. In this state it is dense 

 and hard, but may be separated and rolled out so as to form a sheet 

 resembling leather. It has many interesting and peculiar properties. 

 Insoluble in water and in alcohol, it dissolves in ether, in the sulphuret 

 of carbon, the fat oils, and the liquid carburets of hydrogen. 



It is soft and elastic at the ordinary temperature, but at the tem- 

 perature of 2 above the freezing point it acquires the hardness of 

 wood. A temperature of 100 softens it without altering its form. 

 It then unites with itself with the greatest facility, and two pieces 

 recently cut apart re-unite so as to render it impossible to discover 

 where the junction has taken place. But a higher temperature, 

 approaching 150", changes it into an adhesive substance, which on 

 cooling does not recover the primitive properties of Caoutchouc. 



In the state of recent coagulation, aud while still in a pulpy con- 

 dition, Caoutchouc possesses a degree of plasticity which admits of its 

 receiving, by means of moulds, the most varied forms. 



The greater part of the Caoutchouc of commerce is obtained by 

 the natives of the countries in which it is produced in the form of 

 shapeless masses, collected at the foot of the tree which has been 

 incised or cut for the purpose of extracting the juice from it, or 

 solidified in a trench made in the earth, and coagulated in this rude 

 mould in voluminous masses, which often resemble the trunk of a 

 large tree. A part of it however possesses other forms which the rude 

 art of the natives attempts to communicate to it. They model with 

 plastic clay figures of animals, imitations of the human foot, and 

 p^ar-shaped bodies ; and then dipping these moulds in the thickened 

 Caoutchouc, and renewing the connection when the first coat is 



Q 



