The Heath Tribe. 583 
such as are suitable for the situation where it is wished to 
grow them. But temperature is not the only element of a 
climate. Humidity of the atmosphere and light are other 
elements which must be taken into account. Broadly speaking, 
we may say that all the Ericaceze demand a certain amount of 
moisture in the air surrounding them. This moisture may 
have its source in the mists which frequently envelop the 
mountains where they grow; or it may be due to the vicinity of 
the sea, lakes, marshes, or water-courses. The site and aspect 
for these plants are also of great importance. For those species 
loving a marshy habitat, a low, flat, spongy soil is naturally 
the best; but these species are few in number and less generally 
cultivated than the others. All the other species prefer a 
sloping bank of eastern or northern aspect, but it should be 
sheltered from the winds. If, therefore, there are natural or 
artificial mounds in a garden, the shady side of these should be 
selected for planting clumps of Rhododendrons, ete. In the 
absence of small hills, raised beds can be substituted; but if 
the natural drainage be insufficient, a layer from six to nine 
inches thick of coarse gravel or some other open materia] will 
be necessary in a low situation. 
The site having been selected, and the form of the planta- 
tions decided upon, the natural soil should be taken out to a 
depth of eighteen inches or two feet; and if the subsoil is of 
a heavy impervious nature, a layer of draining materials from 
six to nine inches thick put in at the bottom and filled up 
with peat, roughly broken but not sifted. This earth is thrown 
up into a mound high enough that after sinking it will still be 
a little above the general surface of the ground. The thick- 
ness of this bed will vary according to the size of the species 
it is intended to plant. It will readily be understood that a 
greater depth of soil will be necessary for the large-growing 
Rhododendrons than for those of smaller growth, and such 
as Heaths and Vacciniums. 
In some parts of the country there is a difficulty in pro- 
curing peat, and, besides, a great deal of it is too poor to use 
alone with advantage. It may be enriched by the addition of 
thorougbly rotten leaf-mould with a little sharp sand, ora com- 
" post may be substituted for it consisting of equal parts of sand 
and vegetable mould. But the fibre of the peat being one of 
its important elements, no substitute can equal it. The top- 
spit of earth in an old wood is usually rich in humus and very 
