G8 OUR FARM CROPS. 



tion, however, has been set at rest by recent investigations, 

 which assign distinct characters to the U. Rubigo vero.^ 

 while they confirm the connection between mildew and 

 another form of rust the U. linearis, the so-called 

 spores of which are merely the early stage of the common 

 mildew. 1 Rust and mildew frequently occur together 

 on the same plant, and owing to the diversity of colour 

 in the rust spots they may readily be confounded. 



"Mildew" (tliePuccinia graminis) belongs specifically 

 to a different class of fungi, but the circumstances of its 

 growth, germination, &c., are precisely the same. It 

 differs considerably in external appearance from the 

 "rust" fungus, as the ripe spores of the mildew consist 

 of very small and very dark brown or black coloured 

 club-shaped bodies, having the thicker end divided into 

 two compartments, each filled with sporules. In an early 

 stage of its growth the swollen heads of the filaments are 

 undivided, and it is then known to botanists as the U. 

 linearis. The dark coloured spots or patches of spores 

 (psori) are composed of multitudes of these sporules, which 

 burst through the epidermis of the stem and leaves (to 

 which parts of the plant it is generally confined), fre- 

 quently giving them the appearance of having been par- 

 tially burnt. 



Notwithstanding the great losses sustained every year 

 by the attacks of these fungi, we know at present very 

 little about them, either as regards their mode of attack 

 or their remedies. In 1850, attention was particularly 

 called to this form of disease, by the numerous districts in 

 which it occurred, and by the disastrous effects it pro- 

 duced both on the quantity and the quality of the harvest 

 produce. Where a crop is badly mildewed the yield is 

 frequently reduced one- half, while the value of the small 

 produce obtained is again reduced on the market. The 



1 Berkeley's Cryptogamic Botany, p. 324. 



