AN ENCYCLOPEDIA OF HORTICULTURE. 



445 



Smilax continued. 



never prickly, erect and recurved, or climbing. North America, 

 1699. 



S. h. Simsii (Sims'). I. ovate-acuminate, sub-acute or obtuse at 

 base, small. (B. M. 1920. under name of S. herbaeea.) 



S. lanceolate (lance-shaped), fl. greenish-white ; umbels some- 

 times panicled ; peduncles short, seldom exceeding the petioles, 

 terete. June and July. I. thinnish, rather deciduous, varying 

 from ovate-lanceolate to lanceolate-oblong, narrowed at base into 

 the short petiole, shining above, paler or glaucous beneath, many 

 of them without tendrils. Branches terete, unarmed, h. 16ft. 

 to 20ft North America, 1785. 



S. lattfolia (broad-leaved). A synonym of S. australis. 



S. macrophylla maculata (large-leaved, spotted). A synonym 

 of S. ornata. 



S. marmorea (marbled). A garden name for a plant which 

 probably belongs to S. ornata. 



S. officinalis (officinal). JL unknown. I. oblong, slightly acute 

 at base, abruptly acuminate at apex, mem 



oong, slightly acute 

 branous, 5in. to 7$in. 



long ; petioles 2in. to 5in. long, the margins inflexed, sheath- 

 ing. Young branches sub-cylindric, becoming somewhat quad- 

 rangular, armed with reflexed prickles. Chiriqui, Ac., (about) 

 1866. (B. M. PL 289.) 



S. ornata (adorned).* I. ovate, acuminate, at length cordate at 

 base, freely spotted with silvery-grey on a deep green ground, the 

 marking being confined to the spaces between the veins ; petioles 

 prickly at back. Branches angular, armed with short prickles. 

 Native place unknown, 1865. A handsomely-marked, green- 

 house species. See Fig. 497. (L II. 439.) SYN. & macrophylla 

 maculata. 



S. Pseudo-China (false China). /. greenish ; peduncles two to 

 four times the length of the petioles. July. I. Sin. to 5in. long, 

 ovate-cordate, or on the branchlets ovate-oblong, cuspidate- 

 pointed, green on both sides, often rough-ciliated, thin, becoming 

 firm in texture. Stems and branches unarmed, or with a very 

 few weak prickles. North America, 1739. 

 S. quadrangularis (four-angled). A synonym of 5. rotundi- 



folia. 



B. rotundifolia (round-leaved).* JL greenish; peduncles 

 flattened, rather longer than the pedicels, few-flowered. June. 

 fr. blue-black, globular. L thin, ovate or round-ovate, entire, 

 2in. to 4in. long, abruptly pointed, mostly rounded or slightly 

 cordate at base. Stem climbing high, armed with scattered 

 prickles. North America. (T. S. M. 610.) SYN. S. guadrangu- 

 laris (W. D. B. 109). 



S. salicifolia variegate (variegated Willow-leaved). I. elliptic- 

 lanceolate, finely marbled with white between the ribs, and thus 

 appearing to be marked with four irregularly-margined, white 

 bands, very ornamental. Branches angular, rarely sub-terete, 

 armed with recurved prickles. Para, 1867. Greenhouse. (L H. 

 521, under name of S. loiirrifolia foliis-variegatis.) 

 S. Snuttleworthii (Shuttleworth's). I. large, cordate, acumi- 

 nate, deep green, marked with confluent blotches of silvery -grey, 

 the young ones purplish at back ; petioles curiously deflexed at 

 base. Columbia, 1877. A free-growing, stove climber. 

 S. temnoides (Black Bryony-leaved). A synonym of S. Bona-nox. 

 SMITHIA (named in honour of Sir James Edward 

 Smith, 1759-1828, F.R.S. and P.L.S., founder of the 

 Linnean Society, author of " English Botany," " Flora 

 Britannica," and other works). OBD. Leguminosas. A 

 genus comprising about a score species of stove herbs, 

 sub-shrubs, or shrubs, inhabiting tropical Asia and 

 Eastern Africa. Flowers mostly yellow, rarely purple or 

 violet streaked with yellow, often in unilateral, axillary 

 racemes ; calyx deeply cut, the lobes connate in two 

 lips ; standard sub-orbicular, shortly clawed ; keel in- 

 curved, obtuse, or slightly rostrate; bracts and brac- 

 teoles scarious or striated, persistent. Pods folded 

 back into the calyx. Leaves impari- or abruptly pin- 

 nate; leaflets small, often falcate, exstipellate ; stipules 

 membranous or scarious, persistent. 8. purpurea, the 

 only species which calls for description in this work, 

 requires culture similar to Mimosa (which see). 

 S. pnrpurea (purple). Jl. purple, the round standard and the 

 wings marked with white spots ; bracts ovate, ciliated ; peduncles 

 bristly, equalling the leaves. Summer. L, leaflets oblong, long- 

 apiculate, ciliated ; stipules adnate, ovate, terminated by a 

 bristle. Stem erect, branched, glabrous. A. 6in. to 12in. East 

 Indies, 1848. Annual. (B. M. 4283.) 



SMOKE. Except in towns, or in the immediate neigh- 

 bourhood of smelting-furnaces and coke-ovens, or (though 

 to a less degree) of brickworks and limekilns, Smoke can 

 scarcely be regarded as hurtful to gardens and planta- 

 tions. Jn and around large cities, particularly in the 



Smoke continued. 



manufacturing districts of England and Scotland, the 

 air is charged with soot, in either a fine or a coarse state 

 of division. The soot consists chiefly of carbon, and 

 along with it small quantities of various compounds 

 (empyrenmatic oils, &c.) formed in the combustion of 

 the fuel. All are familiar with the black coating that 

 settles on everything from an atmosphere polluted with 

 Smoke. This coating upon leaves and twigs is injurious 

 by clogging the stomata, or small openings through 

 which air passes into the tissues; and it also hinders 

 the work of the leaves by shutting out part of the light 

 that they should receive to keep them in health, and to 

 fit them to supply the plants with food. This source of 

 danger can be overcome by keeping the plants clean by 

 syringing, or by washing those that are so delicate as 

 to require special care, and so valuable as to deserve 

 the labour. Nor is the danger so frequent as might be 

 imagined from the prevalence of a black, sooty deposit 

 on plants, even those in greenhouses, since these deposits 

 are far oftener composed of Fungi (Fumago, Ac.) than 

 of soot. Moreover, the presence of Carbonic Acid (the 

 most abundant product of combustion) in the atmosphere 

 is necessary to green plants, of which it is a most 

 important food. 



The real danger to plants in the vicinity of towns and 

 smelting-works arises from the presence, in the gases 

 formed during combustion, of poisonous products, of 

 which Sulphurous Acid gas is by far the worst. Its pre- 

 sence is due to the existence of sulphur in the coal as 

 an impurity. Hardly any coal is free from sulphur; and 

 its compound, Iron Sulphide or Pyrites, may often be 

 seen as a yellow, shining coat on the smooth sides of 

 lumps of coal. The leaves of plants show traces of 

 poisoning by Sulphurous Acid gas, when the proportion 

 in the atmosphere does not exceed 1 in 1,000,000 parts, 

 if exposed to this mixture for a considerable time ; and 

 Stockhardt found that Clover and grasses showed its 

 effects when exposed twice, for two hours each time, to 

 1 part in 40,000, the leaves becoming brown at the tips, 

 and the plants withering. But the experiments are 

 usually carried on with plants in confined air, under bell 

 glasses ; and it must be remembered that, in the open 

 air, plants are seldom exposed to the continuous action 

 of the gas, and that the danger is, therefore, consider- 

 ably less than the amount of gas occasionally contained 

 in the air would indicate. It has been found that the 

 leaves of plants poisoned with Sulphurous Acid gas show, 

 at first, translucent spots between the veins. These spots 

 become dull green, and then brown, dry, and shrivelled. 

 When water is copiously supplied to the roots, drops of 

 water often stand along both sides of the larger veins f 

 of the leaves. Along the veins extend green borders, 

 which form a network in the brown, dry leaves. The 

 cells of the green parts retain abundance of fluid. This 

 green network is an indication of the cause of harm ; 

 and chemical analysis of the leaves affords a proof of 

 the presence of sulphur in excess, and confirms the indi- 

 cation given by the colour. The leaves of Conifers 

 become dull green at the tip ; then this changes into 

 brown-red, sharply separated from the green parts below. 

 But in these leaves the effect is very similar to that of 

 frost, or other causes of injury; and the only certain 

 indication is given by chemical analysis, proving the 

 presence of excess of sulphur. Conifers are found to 

 suffer most severely from the action of the gas, as their 

 leaves are less readily renewed. Herbs, under similar 

 exposure, suffer more than ordinary deciduous trees. 

 Plants are injured less by exposure to the gas during 

 darkness, and least of all during winter, when growth 

 has ceased for a time. Limekilns are not so hurtful as 

 smelting-fnrnaces, since the gas combines with the lime, 

 and forms Sulphate of Lime, which prevents its escape 

 in a hurtful form. Another injurious substance in the 



