OF HORTICULTURE. 151 
Honeydew— continued. 
on the plants, or in their neighbourhood. Sometimes, 
in such case, there is no appearance of disease in 
the leaves that bear it; but, at other times, they be- 
come discoloured, the green colouring matter, or chloro- 
phyll, is destroyed below the shining patches, and the 
leaves may fall off early. Under these circumstances, 
the sweet fluid must be produced in, and exuded from, 
the cells of the leaves without any extraneous producer. 
Its production may, then, be regarded as analogous to 
the secretion of similar fluids in nectaries on various 
green parts of many healthy plants, e.g., on the stipules 
of Beans; but, when carried to excess, it becomes a 
disease. The cause, or causes, of the change are still 
only conjectural; and so also are the means for pre- 
venting and curing attacks. Among grasses, Honey- 
dew may be produced in yet a third way, viz., in the 
development of the Ergot Fungus (Claviceps purpurea), 
so plentiful, in many. years, in the heads of numerous 
species of grasses. In the early stage, before the Ergot 
has yet become conspicuous in the ear, the fungus 
produces a body (Sphacelia segetum) that bears on its 
surface numerous spores, imbedded in a sticky fiuid like 
Honeydew. When the fungus is very plentiful among 
grasses, this fluid is correspondingly abundant. It assists 
in the diffusion of the spores of the fungus, as flies are 
very fond of it, and visit the diseased plants, suck up 
the secretion, and carry it away, with spores imbedded 
in it, to other grasses, where the spores, in their turn, 
may propagate the species. The Honeydews of different 
plants probably vary a little in chemical composition ; but 
all contain a considerable quantity of sugars, including 
Mannite and cane sugar. It is to these that the sweet 
taste is due. Plants covered with Honeydew, whatever 
its origin, are very attractive to insects, especially to 
flies, and, at night, to moths. Several kinds of fungi 
also find it very favourable for their development: 
` hence, plants covered with it are apt to assume a sooty 
appearance, due to the growth in them of black or 
brown fungi (Capnodium, &c.). Particles of soot or 
dust are also apt to stick to the leaves. Such ex- 
traneous substances, along with the secretion itself, 
hinder the healthy processes in the leaf from being pro- 
perly carried on, though the stomata, or breathing pores, 
usually escape being clogged, as they are more abun- 
dant on, if not confined to, the lower surface of the 
leaves, and this is not covered. The abundant exuda- 
tion of sugars must also weaken the plants; but the 
effect is seldom dangerous—a fortunate circumstance, in 
our ignorance of methods of cure. 
HONEY FLOWER. See Melianthus. 
HONEY LOCUST. See Gleditschia triacanthos. 
HONEYSUCKLE. See Lonicera. 5 
- HONEYSUCKLE, AFRICAN. See Halleria 
lucida, 
HONEYWORT. See Cerinthe. | 
HOODED. ‘The same as Cucullate (which see). 
HOODIA (a commemorative name). Syns. Mono- 
thylaceum, Scytanthus. ORD. Asclepiadeæ. A genus 
comprising three remarkable species of greenhouse suc- 
culent perennials, inhabiting Angola and South Africa. 
Flowers large, often solitary, shortly pedicellate ; corolla 
rotate, with a very short tube, and a large, dilated, faintly 
five-lobed limb. Stems fleshy, many-angled, Cactus-like, 
thickly covered at the angles with strong prickles, which 
are dilated at the base. For culture, see Stapelia. 
H. (Bain’s). ° f. produced near the apices of the branches, 
one to three tabar tans short, five-partite ; ents acumi- 
nate; corolla pale buff-yellow, becoming purplish in decay, cup- 
S , about Jin. in diameter; margin with five recurved teeth, 
the apices of the obsolete lobes ; corona double. July. Stems 
numerous from the crown, pe tie cylindric, leafless ; younger 
portion with closely-set, spirally-arranged, laterally-compressed 
AN ENCYCLOPAEDIA 
Hoodia— continued. 
tubercles, ultimately confluent into more or less marked promi- 
nent longitudinal ridges ; tubercles tapering into a stout, some- . 
times deflexed, brown prickle. Karroo, 1875, (B. M. 6348.) ; 
H. Gordoni (Gordon’s). fl. produced near the apices of the 
branches, one to three together, shortl petiolate ; calyx short, 
five-partite ; corolla with a very short abe: lobes pale brownish 
flesh-coloured, glabrous. Stems numerous from the crown, erect 
or somewhat spreading, cylindric, slightly branched, leafless ; 
younger portions with closely-set, spirally-arranged tubercles, 
each with a strong, — prickle swollen at the base. 
Orange River, 1874. (B. M. 6228.) 
HOOKERA. A synonym of Brodiwa (which see), 
HOOP PETTICOAT. ‘See Narcissus Bulbo- 
codium. 
HOP. See Humulus Lupulus. 
HOP APHIS. See Aphides. 
HOP FLEA. See Turnip Ply. 
HOP HORNBEAM. ‘See Ostrya. 
HOPLOPHYTUM CALYCULATUM. See Æch- 
mea calyculata, 
HOPLOPHYTUM CG@LESTIS. See Æchmea 
celestis. 
HORDEUM (the ancient Latin name). Barley. ORD. 
Graminew. A genus comprising about twelve species of 
valnable erect annual (or rarely perennial) grasses, natives 
of Europe, Northern Africa, temperate Asia, and extra- 
tropical America. Spikelets in threes, arranged on òp- 
- posite sides of the rachis, hence forming a bilateral spike. 
Barley is, next to Wheat, the most important grain raised 
in this country. It is principally employed in the manu- 
facture of fermented liquors and spirits. Tradition traces 
its culture back to remote antiquity, the Egyptians sup- 
posing it to be the first cerealea utilised by man. The 
principal species are: H. distichon, Long-eared Barley ; 
H. hevastichon, Winter, or Square Barley; H. vulgare, 
Spring Barley ; and H. zeocriton, the Sprat or Battledore 
Barley, a cultivated form of H. distichon. Probably the 
best species for horticultural purposes is H. jubatum, 
which thrives in any ordinary soil. Very little moisture 
is required. Seeds may be sown in the open ground. 
Fig. 240. HORDEUM JUBATUM, 
H. jub: (bearded). * Sqüirrel-tail Grass, — — 
Ore Oe eee” all spreading, ‘June. A. aft. Nort 
America, 1782. See Fig. 240. 
HOREHOUND (Marrubium vulgare). A hardy her- 
- ‘aceous perennial, widely distributed throughout — 
and Northern Asia, and occasionally found wild in Bri 
