AN ENCYCLOPADIA 
OF HORTICULTURE. — 445 
Smilax—continued. i 
never prickly, erect and recurved, or climbing. North America, 
1699. 
S. h. Simsii (Sims’). l. ovate-acuminate, sub-acute or obtuse at 
base, small. (B. M. 1920, under name of S. herbacea.) 
S., lanceolata (lance-shaped). fl. greenish-white ; umbels some- 
times panicled ; ere aay: short, seldom exceeding the petioles, 
terete. June and July. J. 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. A. 15ft. 
to 20ft. North America, 1785. 
S. latifolia (broad-leaved). A synonym of 8. 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). f. unknown. Z. oblong, a acute 
at base, abruptly acuminate at apex, membranous, Sin. to 74in. 
long; petioles Zin, to Sin. long, the margins inflexed, sheath- 
ing. Young branchés sub-cylindric, becoming somewhat quad- 
rangular, armed with reflexed prickles. Chiriqui, &c., (about) 
1866. (B. M. Pl. 289.) 
S. ornata (adorned).* l. 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 
ed at back. Branches angular, armed with short prickles. 
ative place unknown, 1865. A h ely-marked, green- 
house species. See Fig. 497, (I. H. 439.) Syn. S. macrophylla 
maculata, 
. Pseudo-China (false China). jl. greenish; peduncles two to 
-` four times the length of the petioles. July. l, din. 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. duadrpngiiaris (four-angled). A synonym of S. rotundi- 
Jolig, 
S. rotundifolia (round-leaved).* 
flattened, rather longer than the pedicels, few-flowered. June. 
fr. blue-black, globular. Z. thin, ovate or round-ovate, entire, 
2in. to din. long, abruptly pointed, mostly rounded or slightly 
cordate at base. Stem climbing high, armed with scattered 
padam: North aame (T. S. M. 610.) Syn. S. guadrangu- 
ris (W. D. B. 109 ; 
salicifolia variegata (variegated Willow-leaved), Z. elliptic- 
lanceolate, finely marbled with white between the ribs, and oie 
appearing to be marked with four irregularly-margined, white 
bands, very ornamental. Branches angular, rarely sub-terete, 
armed with recurved prickles. Para, 1867. Greenhouse. (I. H. 
521, under name of S. longifolia foliis-variegatis.) 
S. Shuttleworthii (Shuttleworth’s). l. large, cordate, acurai- 
nate, deep green, marked with confluent blotches of silvery-grey, 
the young ones — at back; petioles curiously deflexed at 
base. Columbia, 7. A free-growing, stove climber. 
S, tamnoides (Black Bryony-leaved). A synonym of §. Bona-noz. 
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). ORD. Leguminose. 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; leafiets small, often faleate, exstipellate; stipules 
membranous or secarious, persistent. S. purpurea, the 
only species which calls for description in this work, 
requires culture similar to Mimosa (which see). 
5. purpurea 
Wings marked with white spots; bracts ovate, ciliated ; peduncles 
—, equalling the leaves. Summer. 1., leafiets oblong, long- 
Bristle. Stom ‘erect, branched, glabrous’ A Gite ie, dest 
Indies, 1848. Annual. (BM. 43)” 
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. In and around large cities, particularly in the 
ji. greenish; peduncles 
(purple). f. purple, the round standard and 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 
(empyreumatic 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, &c.) than 
of soot. Moreover, the presence of Carbonie 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 Stlphide 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 
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 duil 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-furnaces, since the gas combines with the lime, 
and forms Sulphate of Lime, which prevents its escape 
-in a hortful form. ` Another injurious substance in the 
