YALE AGRICULTURAL LECTURES. 39 



ones, like 1850, 1851, and 1855, cause rot ; so do sudden alter 

 nations of temperature for instance, from dry, hot weather, to 

 wet, cold, and windy ; and these changes destroy the cucum 

 ber, squash, melon, tomato, and egg-plant, as well as the potato. 

 The years 1847, 1848, 1854, and 1856, and especially 1852, 

 were favorable ones. 



Soil as well as climate has much to do with the nature of 

 crops. Gravel or loamy soils are best, especially when they 

 contain a large proportion of vegetable matter. Sods or straw 

 laid in the furrow over the seed are good, because they main 

 tain an equal temperature beneath them. It is bad to apply 

 much stable manure or guano. Of exposures a northern is best ; 

 a southern heats too much, and an eastern heats too rapidly 

 after a cold night. Early planting is best, as it gives the plant 

 a slow, hardy growth in the comparatively wet weather early 

 in the season, which fits it better to withstand the sudden 

 transitions of midsummer. 



Early maturing sorts are the surest in bad seasons. Potatoes 

 require deep plowing, and should be subsoiled when a few 

 inches high. Plant six inches deep if your soil be dry, culti 

 vate frequently until the plants are in flower, and never after 

 ward. Plant free-growing sorts tjiree by three feet, to give 

 full quantity of air and light. The pieces of seed should not 

 be less than three ounces in weight, each, and cut them length 

 wise, never across the potato. 



Usual Signs of Disease. A wilted leaf on the young 

 rosettes of the plant, which are the tenderest parts, and first 

 show disease. 2d. Steel-blue points on some of the older and 

 outer leaves, and yellow iron-rust stains on the inner leaves. 

 3d. Mildew, which quickly follows these signs, and which, if not 

 arrested, kills the whole plant. These are the signs of disease 

 produced by cold and wet weather changes. 



The hot, muggy atmosphere causes an intense dark green 

 color in the leaf, with spotted blotches, which soon turn into 

 mildew, and kill the plant. In the case of cool weather, 



