AN ENCYCLOPEDIA 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 (Sphncelia segetum) that bears on its 

 surface numerous spores, imbedded in a sticky fluid 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 Gleditscliia triacanthos. 



HONEYSUCKLE. See Lonicera. 



HONEYSUCKLE, AFRICAN. See Halleria 

 lucida. 



HONEYWOB-T. See Cerinthe. 



HOODED. The same as Cucullate (which see). 



HOODIA (a commemorative name). STNS. Mono- 

 thylaceum, Scytanthus. OED. Asclepiadece. 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. Bainli (Bain's), fl. produced near the apices of the branches, 

 one to three together ; calyx short, five-partite : segments acumi- 

 nate ; corolla pale buff- yellow, becoming purplish in decay, cup- 

 shaped, about 3in. in diameter ; margin with five recurved teeth, 

 the apices of the obsolete lobes ; corona double. July. Steins 

 numerous from the crown, ashy-green, cylindric, leafless ; younger 

 portion with closely-set, spirally-arranged, laterally-compressed 



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, 1876. (B. M. 634&) 

 H. Gordon! (Gordon's), fl. produced near the apices of the 

 branches, one to three together, shortly petiolate ; calyx short, 

 five-partite ; corolla with a very short tube ; 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, slightly-deflexed prickle swollen at the base. 

 Orange River, 1874. (B. M. 6228.) 



HOOKERA. A synonym of Brodisea (which see). 

 HOOF PETTICOAT. See Narcissus Bulbo- 

 codium. 



HOF. See Humulus Lupulus. 



HOF APHIS. See Aphides. 



HOF FLEA. See Turnip Fly. 



HOF HORNBEAM. See Ostrya. 



HOFLOFHYTUM CALYCULATUM. See 2Ech- 

 inea calyculata. 



HOFLOFHYTUM CCELESTIS. See JEchmea 

 ccelestis. 



HORDEUM (the ancient Latin name). Barley. OKD. 

 Graminece. A genus comprising about twelve species of 

 valuable erect annual (or rarely perennial) grasses, natives 

 of Europe, Northern Africa, temperate Asia, and extra- 

 tropical America. Spikelets in threes, arranged on op- 

 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. hexastichon, 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 JUBATUH. 



H. jubatum (bearded).* Squirrel-tail Grass, fl., lateral ones 

 abortive, on a short pedicel, short-awned ; perfect flower bearing 

 a capillary awn, 2in. long, all spreading. June. A. 2ft. North 

 America, 1782. See Fig. 240. 



HORE HOUND (Marrubium vulgare). A hardy her- 

 baceous perennial, widely distributed throughout Europe 

 and Northern Asia, and occasionally found wild in Britain. 



