THE PARASITIC EXOASCEAE. 14& 



has progressed, side by side. He shows that Exoasceae, living 

 on related hosts, agree so closely in their ascogenous forms, 

 that it is evident they are generically related species. On this 

 ground he sets up a genus containing many species, and names 

 it Taphrina. According to the host-plants, this genus is 

 divided into four stems, and from it twenty-five species are 

 separated off as the genus Magmmella. Giesenhagen's systematic 

 division, gives a synopsis of the host-plants and their distri- 

 bution as follows : 



I. Genus. Taphrina : asci club-shaped to cylindrical. 



A. Filices-stQm, on Ferns : asci slender, club-shaped; tapering to 

 both ends, rounded apex, greatest breadth in the upper quarter 

 of the ascus. 



T. cornu cervi (Giesh.) on Aspidium aristatum in East 

 Indies and Polynesia. 



T. filicina (Eostr.) on Aspidium spinulosum in Scan- 

 dinavia and Balkan-peninsula. 



T. LaurcTicia (Giesh.) on Pteris quadriaurita in Ceylon. 



T. fasciculata (Lag. et Sad.) on Nephrodium in South 

 America. 



T. lutescens (Eostr.) on Aspidium Thelypteris in Denmark. 



B. Behda-stem on Juliflorae: asci plump, cylindrical, with 

 rounded apex or even a slight depression there. 



(1) On Ulmaceae: T. ulmi (Johan.) on Ulmus montaTm and 



U. campestris in Central Europe and North America. 

 T. celtis (Sad.) on Celtis australis in North Italy and 

 Switzerland. 



(2) On Betulaceae. 

 (a) On Betula : 



T. alpina (Johan.) on B. nana in Scandinavia. 



T. nana (Johan.) on B. naiia in Scandinavia. 



T. betulae (Johan.) on B. verrucosa, B. pubescens, and B. 



turkestanica in Central Europe, 

 T. hetulina (Eostr.) on B. pubescens, and B. odorata in 



Germany, Denmark, and Scandinavia. 

 T. carnea (Johan.) on B. odorata, B. pubescens, B. nana, 



B. intermedia in Scandinavia, Tyrol, and Silesia. 

 T. bacferiospermum (Johan.) on B. nana in Scandinavia 



and Greenland. 



