PLOWRIGHTIA 211 



which changes to a pale brown colour. At a later stage 

 numerous fruiting pustules push through the lenticels, giving 

 to the bark a rough, warty appearance. These represent the 

 summer or conidial form of fruit, and liberate myriads of 

 minute spores which ooze out in the form of tendrils, and are 

 dispersed wholesale by various agents. At a later stage in 

 the season winter spores are formed, which are disseminated 

 from the dead branches the following season. Nursery stock 

 and full-grown trees are equally attacked, and in most 

 instances killed, as the disease usually girdles the trunk or 

 branch attacked, thereby cutting off the supply of water and 

 food. 



Perithecia about twenty in a stroma, flask- shaped, neck 

 long, asci 8-spored. Spores elliptic-oblong, hyaline, i-septate, 

 9-10X4-5 /*. Summer spores, 2-3X1 p, cylindrical, slightly 

 curved, discharged in curly tendrils as in Cytospora. 



Dr. Murrill considers this disease as of a very serious 

 nature, and writes as follows: 'The chestnut growers of 

 southern Europe should be warned against the importation of 

 any species of Castanea from this country for public or private 

 parks or plantations without inspection by a competent person. 

 The European chestnut is so closely related to our native tree 

 that the fungus would doubtless attack it with equal violence, 

 causing great loss where it is cultivated.' 



Murrill, W. A., Journ. N. Y. Bot. Gard., 7, pp. 143, 203 

 (1906). 



Murrill, W. A., Torreya, 6, p. 189(1906). 



PJiOWRIGHTIA (Sacc.) 



Stroma convex, black, the loculi or imperfect perithecia 

 numerous, in a single peripheral row; asci 8-spored; spores 

 elongated, i-septate, hyaline, or yellowish. 



Closely allied to Dothidea, from which it was separated by 

 Saccardo, his distinction being Dothidea, spores coloured ; 

 Ploivrightia, spores hyaline. This distinction, however, is 

 not a valid one, some species of Dothidea, representing one 

 pole, have quite dark spores, others are only tinged with 

 colour, whereas in Ploivrightia, the other pole of Dothidea, 

 the spores are either pale yellow or colourless. 



Gooseberry black knot. The fungus causing this disease 



