74 SYLVA AMERICANA. 



Du Hamel barked in the spring, no one survived the experiment 

 above three or four years, though many of them generated a 

 portion both of wood and bark, originating at the summit, and 

 descending sometimes to the extent of a foot. 



Diseases. 



Diseases are corrupt affections of the vegetable body, arising 

 from a vitiated state of its juices, and tending to injure the 

 habitual health either of the whole or a part. The diseases that 

 occur the most frequently among vegetables are the following : 

 blight, smut, mildew, honeydew, dropsy, flux of juices, gangrene, 

 etiolation, suffocation, contortion and consumption. 



1. Blight. Blight is a general name given for various 

 distempers incident to corn and fruit trees. The term has been 

 used in a very vague and indefinite manner. The origin of the 

 disease has been variously accounted for. There appear to be 

 at least three distinct species of it. The first originates in cold 

 and frosty winds in spring, which nip and- destroy the tender 

 shoots of the plant, by stopping the circulation of the juices. 

 The leaves wither and fall ; the juices burst the vessels, and 

 become the food of numerous insects, which are often mistaken 

 for the cause of the disease, while they are really an effect of it. 

 The second species originates in a sultry and pestilential vapor, 

 and happens in summer when the grain has attained its full 

 growth. The third originates in fungi, which attack the leaves 

 or stem of herbaceous and woody plants ; but more generally 

 grasses, and particularly the most useful grains. It generally 

 assumes the appearance of a rusty looking powder, which soils 

 the finger when touched. There are several sorts of these fungi, 

 known to farmers under the names of red rust, red gum, &lc. 

 The only means of preventing the effect of blight is proper 

 culture. Palliatives are to be found in topical applications. 



2. Smut. Smut is a disease incidental to cultivated corn by 

 which the farina of the grain, together with its proper integuments, 

 and even part of the husk, is converted into a black soot-like 

 powder. If the injured ear is struck with the finger, the powder 



