73 AeMC«LT»RAL ESSAYS. 



the first instance, is afterwards unable to bear up and floiTrisfi 

 when visited with heavy rains, especially if these set in when 

 the crop is in a critical stage. 



"Whether blight and mildew be considered separately, or 

 viewed as one and the same disorder, appearing at different pe- 

 riods of the plant's growth, we are convinced that both may 

 with truth be reckoned to proceed from an unhealthy atmos- 

 phere, when the crop is in certain stages of its progress to ma- 

 turity. Not only the extent but the very appearance of blight 

 and mildew are entirely governed by the seasons, and that with 

 respect to wheat, the kind sown, whether thin or thick chaffed, 

 has a very considerable effect in lessening or increasing the 

 effects of these baneful disorders ; and that even soil, culture 

 and situation, each have their respective influence. It seldom 

 happens that either blight and mildew are felt in dry warm sea- 

 sons, except i?4 close confined fields, when the evening dewe 

 stagnate, anl remain till they are removed by the meridian sun. 

 On the oJier hand in every moist season, whether cold or warm, 

 blight, mildew and gum, on the ear, are experienced in a great- 

 er or lesser degree. In such seasons thin chaffed wheats ar€ 

 much less injured than those that are thick chaffed, which 

 circumstance is in direct opposition to the doctrine that blight 

 mildew and rust, are brouoht on by parasitical plants or fungi. 



"Soil, culture and situation have in an inferior degree an in- 

 fluence in the growth and progress of diseases. Some soils 

 are naturally so moist at bottom, that dampness issues from 

 them at all times. Superior culture and excessive manuring 

 are apt to cause a crop to be early lodged, in nhich case one 

 disease or other is sure to seize upon it ; and a southern as- 

 pect and every confined situation are much more hazardous 

 than those of a northern or western exposure, and where the 

 air has free egress. In a word, when hoar frost or vapour of 

 any kind is dispelled by wind, no danger will follow to the 

 crop ; but when a hot sun is the agent, we have repeatedly no- 

 ticed the most serious losses.* 



* See Encylopedia on diseases of wheat, page, 277. 



