2 
HOUSTONTA. 
4 
9 
HUMULUS. 
filled with tan in which the plants 
are plunged; but in some cases, 
instead of tan, or any other ferment- 
ing material, there is a cavity be- 
neath the bed, in which flues or pipes 
of hot water are placed; and the 
surface of the bed is either covered 
with sand, or some other material, | 
calculated to retain an equality of. 
moisture, in which the pots are 
plunged in the same manner as in 
the tan. Some cultivators do not 
use any materials in which to plunge 
the pots, but merely set them on the | 
mest common species, H. carnosa, 
surface of the bed, trusting to the 
general heat of the air of the house, 
or the heat emitted through the bot-_ 
tom of the pit from the pipes or. 
quires a light rich soil, and is propa- 
'gated by cuttings, which, however, 
flues below, taking care to keep the 
surface of the bed on which the 
pots stand moist by pouring water | 
over it at least once a day. The 
heat of hothouses for ordinary tro- 
pical plants should at no period of 
the day or year be lower than 65°; 
but in summer, during bright sun- 
shine, it may be as high as 70°, 80°, 
or 90°. Daring 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 
or the ordinary plants of the tro- 
pics, and also a_ proportionately 
great degree of moisture ; and in 
order to attain the latter object, 
the floor of the house, or the hot- 
water pipe, should be frequently 
sprinkled with water. 
Horro\nta.—Primuldcee. —The | 
Feather Foil, or Water Violet. An | 
aquatic British plant, which pro- 
duces a pretty effect from its pink 
flowers, on the borders of ponds and 
ditches, where the soil is gravelly. 
Hounn’s Toneue.—See Cyno- 
GLO’SSUM. 
House Lerx.—See Semrervi'vum. 
Housro'niaA.— Gentianee.— Pret- 
ty little plants, natives of North 
America, and suitable for rockwork. 
They should be grown in peat soil 
kept moist, and they are propagated 
by dividing the roots. 
Ho'vea.— Leguminose.—Beauti- 
ful dwarf shrubs, natives of Aus- 
tralia, which require a greenhouse 
in Great Britain. They should be 
grown ina mixture of sandy loam 
and peat; and they may be propa- 
gated 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. 
Ho'ya. —— Asclepiaddeee. — The 
has curious wax-like flowers, from 
which drops a sweet, honey-like juice. 
It is a hothouse climber, which re- 
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 
covering, thrown over the roof of 
the house in severe weather. 
Hupso\n1a. — Cistinee. — 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. 
Hou'mea.— Composite. — Elegant 
biennial plants, which should be 
/sown on a slight hotbed in spring ; 
then potted off and kept in the open 
air during summer, and in the green- 
house during winter, to be finally 
planted in the open border in May 
the second year. If the plants are 
repotted three or four times during 
the course of the first summer, al- 
ways into only a little larger pots, 
they will become so much stronger 
before they are finally planted out 
as amply to ae io the additional 
trouble. 
Hu'muwvs. — Urticdcea. — The 
Hop. This plant, though generally 
