WILD WALL-GARDENS 233 



crevices, as the rooks will in the turf of the open fields and 

 downs. But field-mice climb old walls freely, by the help 

 both of fruit-trees and ivy ; and they are great hoarders and 

 forgetters of the food harvested in their nocturnal wander- 

 ings. Rats sometimes form regular runs to the tops of walls, 

 especially when they are helped on their way by inner 

 crevices and fractures ; and they too are liable to drop or 

 forget their booty, or to be killed before they can reap the 

 results of their care. 



The soil of the wall-garden is partly produced by the 

 decay of the mortar and softer brick or stonework under 

 frost and rain, and is partly a vegetable mould formed by 

 decaying mosses and lichens. The mixture of this kind of 

 leaf-mould with the calcareous weathering of limestone walls 

 forms a soil which though scanty is kindly, and where both 

 sunshine and rain are abundant the wall-garden throughout 

 the summer is delicately gay. The thoroughness and secrecy 

 of nature's system of seed distribution are emphasised by the 

 sureness with which wall-flowers appear in course of time on 

 an old garden-wall. Their small heavy seeds are certainly 

 not wind-blown to each new site ; we can only judge that 

 they are carried by birds, like the currant and haw. Several 

 of the finches, which feed variously on seeds in late summer 

 and autumn, may well be distributors of the wall-flower ; but 

 there is no positive knowledge of this link in the garden 

 chain. In their freedom from the control of the gardener, 

 wall-flowers in the wild wall-garden tend steadily to return 

 to their ancestral type, like London pigeons. The lemons 

 and freaked scarlets disappear, and the stalwart tufts of the 

 wall deepen to orange-brown and crimson. A native of dry 

 cliffs the wall-flower thrives better on its spare new soil than 

 such plants as the elder or the apple-tree. Its blossoms 

 shoot dense and lusty, and shed a warm tide of scent in the 



