476 



FUNGI IMPERFECTI. 



of the shoots, and either rupture the epidermis or grow out from 

 the leaf-scar cushions (Fig. 297). The conidia are abjointed 

 from filamentous conidiophores inside the pycnidia, and emerge 

 as tendril-like structures. They are two-celled, small, cylindrical, 



and pointed at both ends. 

 Germination takes place 

 easily in water, and the 

 disease spreads rapidly over 

 the young developing shoots 

 during May. The mycelium 

 permeates the twig, living 

 both inside the cells and 

 between them. 



The disease has been 

 observed on Picc/t c.ccdsa 

 and P. Menziesii, not only 

 in nurseries and on youn" 



\i o 



trees, but also in pole- 

 forest, where it frequents 

 the upper crown and causes 

 death. At the beginning 

 of an attack the pruning 

 of diseased twigs in young- 

 plantations should be at- 

 tended to. 

 Septoria rubi (Westend.). 1 Blackberry leaf-spot. This is a 



parasite of some economic importance in the United States, where 



it interferes with the blackberry culture. It also occurs in Europe 



and Britain. 



S. ribis Desm. produces a somewhat similar disease on leaves 



of currant and gooseberry. 2 (Britain and U.S. America.) 



S. piricola Desm. occurs throughout all Europe, causing little greyish 

 s| mts on leaves of pear trees. It is probably a pycnidial form of Sphoerella 

 lucillac Sacc. 



S. crataegi Kich. A common species on leaves of Crataegux in Europe. 



S. cerasina Peck. On leaves of Primus serotimi in the United States. 



Many forms of S<'i>f<>rin infest cultivated vegetables : 



S. petroselini Desm. is the cause of dry spots appearing on leaves of 



Fid. 296. Sfploria jni,-ii.<itii-n. a, Young diseased 

 shout of Spruce, with apex still fresh and green. 

 b, Needle diseased towards base, c, Apex of a two- 

 year-old shoot, into which the disease has extended 

 backwards from the younger shoot ; the brown 

 discoloration of cortex and pith is indicated by 

 shading. (After R. Hartig.) 



1 Description in Bulletin, No. 6, Ohio Ar/ric. Ex per. ftfafioii, 1S91. 

 2 Description in Bulletin, No. 13, loica A<jric. Exper. Station, 1891. 



