240 DISEASES OF CULTIVATED PLANTS 



caused by Guignardia vaccinii. It first appears as a small 

 light-coloured spot, the whole berry becoming soft. At a late 

 stage small dark-coloured blotches appear on the inner 

 surface of the skin of the fruit. The leaves are also attacked. 

 The disease proves very destructive in various parts of the 

 United States. 



Perithecia scattered, the black beak, beset with continuous 

 black spines, only bursting through the cuticle, 300-400 fi 

 diam. Asci clavate, 8-spored, accompanied by paraphyses. 

 Spores hyaline, then yellowish-brown, elliptic-oblong, 27-36 x 

 12-20 //. 



The spores are ejected from the asci in a compact mass 

 enclosed in mucilage, as in many species of coprophilous 

 fungi. 



Treatment the same as for cranberry scald. The two 

 diseases usually occur together. 



Shear, C. L., U.S. Dipt. Agric, Bureau of Plant Industry. 

 Bull. No. 1 10, (1907). 



E. Spores coloured, \-septate. 



DIDYMOSPHAERIA (Fckl.) 



Perithecia covered by the epidermis, which remains un- 

 changed or is blackened ; asci 4-8-spored, with paraphyses ; 

 spores elongated, 1 -septate, coloured. Spermogonia and 

 pyenidia frequent 



Poplar twig disease. Prillieux states that in certain parts 

 of France, poplars, more especially the pyramidal poplar, 

 becomes covered with dead shoots, or frequently completely 

 perishes. This has been attributed to various causes, as 

 c instant reproduction by cuttings, etc. The injury is in 

 reality caused by a fungus named Didymosphaeria populina 

 (Vuill.). The tips of the young shoots are killed ami blackened. 

 Infection takes place when the shoots are quite young, and is 

 indicated by the curving and shrivelling of the tips ; finally 

 the young shoot perishes, and lateral uninjured shoots take 

 their places. When a tree is once infected this killing of 

 many terminal shoots occurs every spring, which weakens the 

 tue, the effect being ultimately shown in the death of the 

 crown. Pyenidia in immense numbers on the blackened 



