CULTIVATION. 
387 
caused tlie garden to become drier, as is manifested 
by tbe disappearance of above nearly forty species of 
Mosses, Hepaticce, and Lichens; tbe effects of this, with 
other causes, liave been hurtful to the hardy Fern col- 
lections. In forming a new rockery, after the plants 
have become once established, as few changes should 
take place as possible, either with the plants or stones 
on which Mitsci should be encouraged to grow ; and 
in order to give a decorative effect, Sedums, Sempcr- 
vivums, Saxifrages, &c., may be placed on the pro- 
jections and shelvings of the stones, the whole bordered 
by a line of spring-flowering plants, such as Iberis 
sempervirens, Alyssum saxatile, Arabis alpina, and 
other plants of that nature. 
It may be also mentioned that the vicinity of water 
is a favourable position for a Fernery; where such 
does not already exist, an artificial piece of water 
should be made in conjunction with the rockery, 
varying in size from a small basin to any extent : it 
may be circular, oblong, straight, or winding, with 
irregular projections. In ordinary cases its width need 
not exceed ten to twelve feet ; its margin should con- 
sist of a bog or border, not less than three feet wide, 
having a slope to the edge of the water. This border 
will afford the means of growing a great many curious 
sub-aquatic and bog plants, and the projections will 
be excellent positions for the different species of 
Osmunda ; water-lilies occupying the centre. 
The want of such a rockery and aquarium has been 
much felt at Kew; for with all the great cost for 
lakes, ponds, and water-works, yet no arrangement 
has been made for growing a scientific collection of 
bog and aquatic plants, either hardy or tropical. 
2 c 2 
