74 THE DISEASES AND ACCIDENTS OF PLANTS, 



woven or set together, from 24 to 36 inches in height. To present a 

 straight or wall-like boundary, three fences two or three yards apart 

 are sometimes placed parallel to each other. The outer fence may 

 consist of iron posts and rods, no closer together than is necessary to 

 exclude horses, cattle, and deer ; the second fence should be such as 

 will exclude sheep ; and between this fence and the outer one there 

 may be several large bushes, or low trees, with branches reaching to 

 within the height of a sheep from the ground. The third fence need 

 not be more than two feet high, with an iron wire about a foot higher 

 along the top, and with the wires sufficiently close together to exclude 

 hares and rabbits ; and between this fence and the sheep-fence there 

 may be several shrubs with their branches resting on the ground. 

 Thus, by the distribution into three fences of the materials which 

 commonly form one fence, the outer margin of the plantation may be 

 made to appear as free and irregular as if there were no fence at all. 

 See fig. 11. 



The chief objection to such a mode of breaking up a straight 

 boundary line with picturesque beauty is the expensiveness of the 

 fencing. The same object may often be gained by planting groups of 

 trees and shrubs inside a single line of fence, or where a distant view 

 is desired, a sort of ha-ha may be dug out the depth of the fence, 

 which renders the boundary invisible. 



CHAPTER V. 



THE DISEASES AND ACCIDENTS OF PLANTS, IN THEIR 

 RELATION TO HORTICULTURE. 



THERE are various diseases and accidents to which plants are liable, 

 some of which are beyond the control of the gardener, and others he 

 can avert or subdue. The principal diseases which affect garden 

 plants are the canker, mildew, gum, honey dew, and flux of juices. 



The canker chiefly affects apple and pear trees, and of these some 

 varieties of apples are constitutionally more liable to this disease than 

 others for example, the Rlbston Pippin. The canker exhibits itself 

 in small brown blotches, which afterwards become ulcerous wounds, on 

 the surface of the bark, and soon extend on every side, eating into the 

 wood, and sooner or later becoming so large as ultimately to kill the 

 tree. The causes generally assigned are, the unsuitableness of the 

 soil, the unpropitiovisness of the climate, and the unfavourableness of 

 the seasons ; and here the matter generally rests. But soil and climate 

 alike may be improved, and even the severity of the season modified, 

 by drainage and proper cultivation. The chief causes of canker are a 

 wet bottom, deep planting, and the use of rank manure. 



To prevent canker all these conditions should be reversed. The 

 soil should be a good friable loam, two feet or more in depth, resting 

 on a dry bottom. Care must also be taken to keep the collar of the 



