HOUND S TONGUE. 



14 4 



HUMEA. 



no period of the day or year be lower 

 than 65° ; but in summer, during 

 bright sunshine, it may be as high as 

 70°, 80°, or 90°. During winter it 

 should never be lower than 60° in the 

 day-time. In hothouses devoted to 

 the growth of Orchideous plants, a 

 higher temperature is requisite than 

 for the ordinary plants of the tropics, 

 and also a proportionately great de- 

 gree of moisture ; and in order to at- 

 tain the latter object, the floor of the 

 house, or the hot-water pipe, should be 

 frequently sprinkled with water. Such 

 houses, from their intense heat, are 

 commonly unpleasant to remain in for 

 any length of time ; but this inconve- 

 nience is avoided by producing a free 

 circulation of the air, which, when in 

 motion, even though the temperature 

 is 70° or 80°, is by no means more in- 

 convenient than that of a greenhouse 

 with the air at 60°, and at rest. This 

 motion is produced by having the heat- 

 ing pipes in a flue or tunnel at the back 

 of the house, or indeed in any part of 

 it, and conducting large air-tubes from 

 this flue or tunnel to the highest part 

 of the house. From the opening of 

 the tubes the heated air is emitted and 

 diffused through the house; while un- 

 derneath the floor there are horizontal 

 tunnels communicating with the tun- 

 nel containingthehot-waterpipes, with 

 gratings over them at their farther 

 extremities, by which gratings the air 

 of the house is drawn in, to be re- 

 heated by the hot- water pipes, and 

 re-emitted by the upper extremities 

 of the tubes which proceed from them. 

 This mode of heating is the invention 

 of Mr. Penn, of Lewisham, 



' HotWnta. — Primulacece. — The 

 Feather Foil, or Water-violet. An 

 aquatic British plant, which produces 

 a pretty effect from its pink flowers, 

 on the borders of ponds and ditches, 

 where the soil is gravelly. 



Hound's Tongue. — See Cyno- 

 glo'ssum. 



Housr Leek. — See Sempervivum. 



Housto^nia. — Gentianece.--~Pvetty 

 little plants, natives of North Ame- 

 rica, and suitable for rockwork. They 

 should be grown in peat soil kept 

 moist, and they are propagated by di- 

 viding the roots. 



HoVea . — Leguminbscs. — Beauti- 

 ful dwarf shrubs, natives of Australia, 

 which require a greenhouse in Great 

 Britain. They should be grown in a 

 mixture of sandy loam and peat ; and 

 they may be propagated by cuttings, 

 which are rather difficult to strike ; 

 and which should therefore be put 

 under a bell-glass, in pure sand, and 

 plunged into a hotbed. 



HVya. — Asclepiadacece. — The 

 most common species, H. carnosa, 

 has curious wax-like flowers, from 

 which drops a sweet, honey-like juice. 

 It is a hothouse climber, which re- 

 quires a light rich soil, and is propa- 

 gated by cuttings, which, however, 

 will not strike without the help of 

 bottom-heat. It is sometimes grown 

 in greenhouses, if in a warm situa- 

 tion, exposed to the sun. In this 

 case, it should be trained close to the 

 glass, and a mat, or some other cover- 

 ing, thrown over the roof of the house 

 in severe weather. 



Hudso'nia. — Cistinece. — North 

 American heath-like shrubs, nearly 

 allied to the Helianthemums, which 

 require protection in England dur- 

 ing winter. They should be grown 

 in peat, and they are propagated by 

 cuttings struck in sand. 



Hu v mea. — Composites. — Elegant 

 biennial plants, which should be sown 

 on a slight hotbed in spring ; then pot- 

 ted off and kept in the open air during 

 summer, and in the greenhouse dur- 

 ing winter, to be finally planted in the 

 open border iD May the second year. 

 If the plants are re-potted three or 

 four times during the course of the 

 first summer, always into only a little 

 larger pots, they will become so much 



