PHOMA. 469 



Ph. malvacearum West. On mallows and hollyhock in Europe. 



Ph. longissima (Pers.). In species of Umbelliferae and Chenopodiaceae 

 iu Europe and America. 



Ph. errabunda Desm. In stems of Verbascum. (Britain.) 



Ph. cucurbitaceanim (Fr.). On fruits of various species of Cuour- 

 bitaceae in Europe and America. 



Dendrophoma. 



Pycnidia similar to Phoma, conidiophores however bearing 

 several conidia either on branches or little processes 



Dendrophoma Marconii Cav. attacks Hemp (Cannabis sativa), 

 causing dark oblong spots on the green stem. The pycnidia 

 are embedded and break through the epidermis with a round 

 pore. The conidiophores are branched, with swollen ends 

 carrying little short rod-like unicellular conidia. In case of 

 attack, which generally occurs towards the close of the 

 vegetative period of the hemp, it is suggested to cut the 

 crop somewhat prematurely, and thereby prevent maturing and 

 spreading of the fungus. 



D. convallariae Cav. produces dark elongated spots on leaves of Con- 

 "oallaria majalis. 



D. valsispora Penz. is recorded by Penzig on living leaves of Citrus 

 Limonum (Lemon). 



Sphaeronaema. 



Pycnidia embedded, membranous, and long-beaked. Conidia 

 ovoid or oblong, unicellular, and almost colourless. 



Sphaeronaema fimbriatum (Ell. et Hals.), (Ceratocystis 

 fimhricUa Ell. et Hals.). Black rot or black shank of sweet 

 potato.^ The parasite shows itself as black depressed spots on 

 the lower parts of young plants, and these may extend over 

 the whole shoot. The disease is best recognized on the tubers, 

 where it consists of dark, somewhat greenish spots, varying 

 from ^ to 4 inches in diameter, and extending some distance 

 into the tissue. These spots when once seen cannot be mis- 

 taken, as they are sunk areas with distinct margins, like spots 

 burned into the potato with a piece of metal which has left 

 the skin uninjured. The mycelium consists of thick-walled 

 olive-brown hyphae, which cause death and destruction to the 



'Halsted and Fairchild, Jour, of Mycology, Vol. vii., 1891, with Figures. 



