CULTIVATION. 353 



caused tlie garden to become drier, as is manifested 

 by the disappearance of above nearly forty species of 

 Mosses, Hepatlcce, and Lichens; the effects of this, with 

 other causes, have 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 Musci should be encouraged to grow ; and 

 in order to give a decorative effect, Sedums, Semper- 

 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 A 



