HYD 



C 



HYO 



Hydrophyte [Hydrophylaceas]. Linn., 5- 

 Pentandria 2-Diyynia.} 



Greenhouse herbaceous plants. Divisions, cut- 

 tings, and seeds; spino'sa is a small aquatic, grow- 

 ing best in peat and loam; quadrlva'luis is also 

 found in boggy places. 



H. quadriva'iois (four-divided). Pale blue. July. 

 Carolina. 1824. 



spino'sa (thorny). 1. Blue. S. Amer. 1791. 



HYDEOME'STUS. (From Jiydor, water, 

 and mestos, half; referring to the plant 

 living in water during the rainy season. 

 N&t.ord.iAcanthads [Acanthacese]. Linn., 

 I4:-Didynamia 2-Angiospermia. ) 



Stove evergreen shrubs. Cuttings of young 

 shoots any time in spring and summer, in sandy 

 soil, and bottom-heat ; peat and loam. Summer 

 temp., 60 to 80 ; winter, 48 to 55. 

 H. macula'tus (spotted). 2, Yellow. May. 

 Mexico. 1842. 



HYDEOPE'LTIS. ( From hydor, water, and 

 pelte, a shield ; referring to the floating 

 shield-like leaves. Nat. ord., Watershidds 

 [Cabomhacese]. Linn., I3-Polyandria 6- 

 Polygynia.) 



A very neat little hardy water-plant, well worth 

 growing by the edges of an aquarium, round a 

 mass of water-lilies, its nearest allies. Division ; 

 marshy soil ; should be protected in winter. 

 H.purpu'rea (purple). Red. July. N. Amer. 1798. 



HYDKOPHY'iATna. Water-leaf. (From 

 hydor, water, and phyllon, a leaf. Nat. 

 cx&.tHydrophyls [Hydrophylacese]. Linn., 

 5-Pentandria 1-Monogynia. Allied to No- 

 nophila.) 



Hardy herbaceous perennials, from North Ame- 

 rica. Divisions and suckers ; rich loam and peat ; 

 in marshy situations. 



H. appendicula'tum (appendaged-caty*e<Z). |. 

 Blue. May. 1812. 



Canade'nse (Canadian). . White. May. 1759. 



Virgi'nicum ( Virginian). . Blue. June. 1739. 

 HYDBOTJE'NIA. (From %dor, water, and 



tainia, a band ; referring to a triangular 

 band in the flower secreting a liquid. 

 Nat. ord., Irids [Iridacese]. Linn., 3-Tri- 

 andria l-Monogynia. Allied to Beatonia.) 

 A pretty half-hardy bulb, with the aspect of a 

 Tigndia, and flowers like a Fritillaria. Seeds, 

 sown when ripe, or kept, and given a little heat in 

 the spring ; division of the offsets ; light, rich, 

 sandy loam ; taken up, and kept after the foliage 

 is decayed, and planted out the following spring. 

 If left in the ground, and covered to protect from 

 rains and frosts, the plants will be stronger than 



ie bulbs were kept dry all the winter. 

 H. loba'ta QobeA-flowered) . ij. Yellow, purple. 



, May. Lima. 1843. 



tnelea'zris (Guinea-fowl-like). 1. Yellow. July. 

 Mexico. 1837. 



HYGROMETER. An instrument for as- 

 certaining the quantity of moisture in the 

 air. Everything that swells by moisture, 

 and contracts by dryness, is capable of 



being formed into one. Every gardener, 

 who has taken a cool bunch of grapes 

 into a hothouse well-supplied with mois- 

 ture, would, in the grapes almost instantly 

 being covered with dew, see the principle 

 upon which the hygrometer acts. The 

 colder the grapes, the warmer the house, 

 the more the vapour contained in it, the 

 sooner would the dew be formed, and the 

 more plentiful its depositure. Pouring 

 cold water into a glass tumbler, in similar 

 circumstances, will be attended with, a si- 

 milar result : dew will be deposited on the 

 outside of the glass ; because, in either 

 case, the cold body condenses the vapour 

 in its neighbourhood ; and this is what is 

 called the dew point, being that tempera- 

 ture at which moisture is deposited from 

 the surrounding atmosphere upon any 

 object of that particular temperature. The 

 drip in frames, greenhouses, &c., is simi- 

 larly caused. The thermometer is the best 

 instrument for showing the temperature ; 

 and by taking two similar ones, covering 

 their bulbs with a fold of muslin or silk, 

 keeping one dry and the other wet, with 

 a thread of flos-silk acting as a syphon 

 from a 'vessel of water, the greater the 

 difference of temperature indicated by 

 the moist and dry thermometer, the 

 greater the deficiency of atmospheric 

 moisture. The nearer the temperature 

 of the moist and dry bulb, the nearer is 

 the air to being saturated with moisture. 

 To obtain more perfect details Daniel's 

 Hygrometer is the best instrument. It is 

 represented in the following figure. It 

 consists of two hol- 

 low glass balls con- 

 taining ether, and 

 communicating by 

 the glass tube 

 which rests on the 

 support. The ball 

 which forms the 

 termination of the 

 longer leg is of 

 black glass, in or- 

 der that the forma- 

 tion of clew on its 

 surface may be the 

 more perceptible. 

 It includes the bulb 

 of a delicate thermometer dipping in the 

 ether, its scale being inclosed in the tube 

 above the ball; and whatever change 

 takes place in the temperature of the 

 ether is indicated by this thermometer. 

 The other ball is covered with zraslua. 



