DIVISION OF GARDENS AND GROUNDS. 45 



growth of the fungus ; we only know that shelter and protection will 

 prevent it, and of this we have seen many proofs, both incidental and ex- 

 l)crimental. It is not unusual to find in fruit exhibitions in cities sam- 

 l)les of the "White Doyenne pears as fine and as free from cracking as 

 liny variety that could bo named ; these fruits have been gathered from 

 trees growing in sheltered city yards which have received no special 

 care or indeed culture of any kind. 



Several espcrimeuts have been recorded which tend to prove that the 

 cause is climatic ; of these may be mentioned that of a dwarf tree of tL<; 

 White Doyenne, which produced abundantly of cracked fruit when in 

 the open garden, but which, when removed and planted in a box in a 

 cool greenhouse, ripened perfect, smooth-skinned, fine fruit. Another 

 is that of a grower who had a row of dwarf pear trees of this variety 

 which produced worthless, cracked fruit ; of these, two were partially 

 inclosed by glazed hot-bed sashes, four of which were set on end around 

 the tree, thus forming a square inclosure open at top 5 these were ele- 

 vated about 18 inches from the surface of the ground, so as to include 

 the larger portion of the top of the trees. Trees thus protected pro- 

 duced fruit perfectly free from any symptoms of cracking, while contigu- 

 ous trees were so badly attacked as to produce comparatively worthless 

 fruit. This experiment was repeated for several years, each year the 

 sashes being removed and placed on different trees, and always with 

 the same result, the protected trees yielding perfect fruit, while those 

 not protected were all more or less injured by cracking. 



These observations and experiments prove that the cause of the 

 cracking of the pear is climatic, and tliat the culture of the soil, or, so 

 far as is at present known, applications to the soil, have ho effect what- 

 ever in preventing this disease. 



THE ROT OF THE POTATO. 



The potato rot is caused by a fungus, Peronospora infestans. This is 

 closely allied to the gxape-leaf mildew, Feronospora viticola, and is un- 

 doubtedly fostered by similar atmospherical conditions. 



The mUdew of the potato first attacks the foliage of the plant, form- 

 ing patches on the under side of the leaves, and, under favorable condi- 

 tions, it spreads rapidly and in a short time reaches the stems, the fun- 

 gus thread running down through them to the tubers, which soon com- 

 mence to decay. 



When potatoes are planted on flat, low-lying lands, they will soon cover 

 the surface with a thick, heavy mass of stems and leaves, and when 

 heavy dews prevail they become saturated with water, and their mas- 

 siveness prevents the complete evaporation of moisture during the day, 

 so that, as long as dews prevail, they never become thoroughly dry. 

 The same conditions will occur during a i^eriod of dull and Tuiuy 

 weather. Under these circumstances the fungus grows rapidly, and if 

 not checked it speedily destroys the crop. 



The rot will appear even on dry lands, if they are sufficiently rich to 

 cause luxuriant growth, and the situation low. On hill-sides the rot is 

 not so virulent, because in these positions dews are not so prevalent, 

 and are at all times slight, compared with the heavier dews in valleys ; 

 the moisture is quickly evaporated on hill-sides, owing to the better ex- 

 posure to sun and to the movements of the air, just as, grape culture is 

 more certain, and the liability to mildew reduced to a minimum, on ele- 

 vated sites. 



The practical deductions proceeding from the above considerations 



