FUNGOID PESTS OF CULTIVATED PLANTS. 133 



the rust of Peach leaves and not now with the usual form on the leaves 

 of Plum, and it is our pleasure to treat them as distinct diseases. 



The underside of Peach leaves is liable to be affected with a rust the 

 pustules of which are small and numerous. The cuticle is soon split, and 

 the spores scattered as a fine rust-coloured dust. The form of these 

 spores is quite unusual for those of a uredo, but approaching the type 

 which is common in the teleutospores of Uromyces. They are consider- 

 ably elongated, swollen in the middle, and almost bluntly lance-shaped, 

 quite smooth externally, with the coat of the spore considerably 

 thickened at the apex, and continued at the base into a rather short thick 

 pedicel (35-40 x 12 p). In fact, more like the teleutospores of Uromyces 

 than the uredospores of Puccinia. 



Latterly it has been suggested that these Uromyces spores are a third 

 kind of spore, called " amphispore," constituting the cycle of Puccinia 

 Pruni, several instances now being known in which uredospore, amphi- 

 spore, and teleutospore are produced in succession. 



This rust is more common in the United States than it is with us 

 but it is found also in Southern Europe and in Australia. 



Cooke in Bav. Fungi Exsicc. ; Cooke Hdbk. Austr. Fungi, No. 

 1734 ; see also Gard. Chron. Dec. 17, 1904, p. 418. 



Peach-leaf Blister. 

 Exoascus deformans (Berk.), PI. XL fig. 23. 



Peach-leaf blister is such a common affection that a description is 

 scarcely necessary. Sometimes aphides or other small creatures may 

 produce somewhat similar appearances, but the real Peach blister is an 

 established fact. 



The leaves are puffed up, blistered, and contorted in a variety of ways, 

 and this disfigurement will proceed until it spreads gradually over the 

 entire tree unless it is checked at once. 



The under surface of the leaves, in the hollows of the blisters, 

 assumes a hoary or frosted appearance, and when examined under the 

 microscope is found to consist of a number of cylindrical cells formed of 

 a transparent membrane closely packed together side by side, each cell 

 or ascus containing the elliptical sporidia (7 x 5 /j.) in the same manner as 

 in the Pear blister and in the Plum pockets. 



This disease is sometimes called the " curl," from the curling and 

 distortion of the leaves. 



Diseased or fallen leaves should be burned. Branches bearing 

 diseased leaves should be pruned back beyond the point of infection. 

 The disease is rampant if the leaves receive a sudden check from fall of 

 temperature. Activity of the disease has been checked by a sudden 

 increase of temperature. 



Known in France, Germany, Belgium, Sweden, Austria, Italy, 

 North America, South Africa, Algeria, Australia, China, and Japan. 



Gard. Chron. July 9, 1887 ; Mass. PL Dis. 82, fig. 11 ; Cooke 

 Hdbk. No. 2233 ; Berk. Outl, p. 376, t. i. f. 9, a. 6 ; Sacc. Syll. viii. 3341 ; 

 McAlpine Fung. Dis. p. 13 ; Journ. Q.M.C. 1904, p. 58 ; Joum. B.H.S. 

 xxix. p. 856 ; Gard. Chron. May 13, 1905, p. 294, fig. 121. 



