A NEW DISEASE ON THE LARCH IX SCOTLAND. 20I 



Klebahn,^ by infection experiments commenced in 1896 in the 

 neighbourhood of Hamburg, conclusively proved that Perider- 

 miuin Laricis is the scidial condition of Melatnpsora betuli?ia. 

 In his earlier experiments spermogonia were formed on Larix 

 etiropcea as the result of infection by teleutospores from the birch, 

 but in later investigations aecidia only were produced. 



Melampsora betulina differs from the remaining species of the 

 genus in the presence of a pseudoperidium enclosing the uredo- 

 spore sorus. Klebahn has therefore instituted a new genus, 

 Afelampsoridimn, for the reception of this species. The differ- 

 ences between the two genera are as follows : — 



Melampsoridtum : ^Bcidium of the Pen'den?iium type. 

 Uredospore sorus with a definite pseudoperidium. 



Melampsora : ..^cidium of the Cceoma type. Uredospore 

 sorus surrounded by capitate hairs, but without a definite 

 pseudoperidium. 



The teleutospore sorus is similar in each genus. 



Arthur and Kern include Feridermiiem Laricis in their list 

 of North American species, since Melampsoridium betulinum is of 

 common occurrence in that country ; the stage on the larch has 

 not yet, however, been found in North America. Saccardo (Sylloge 

 Fungonim, xxi.) records its occurrence in France and Germany. 



The specimens of Peridermium Laricis obtained in Scotland 

 differ in some respects from those described by Klebahn. Up to 

 the present no spermogonia have been discovered ; it is possible, 

 however, that these develop earlier than the aecidia, and have, 

 in consequence, been overlooked. The colour of the pseudo- 

 peridium is described by Klebahn as bright red-orange ("hell 

 rotlich-orange "). In the Scottish specimens, in the early stages 

 before the pseudoperidium had opened, the colour was pale 

 yellow, and, after dehiscence, it became white. 



Considering the abundance of Melampsoridium betulinum in 

 this country, it is a remarkable fact that Peridermium Laricis is 

 of such rare occurrence. Its resemblance to Cceoma Laricis may, 

 however, partly explain the absence of previous records. It is 

 possible that Melampsoridium betulinum really consists of several 

 physiological species, and that Peridermium Laricis is only one 

 of its recidial forms ; this supposition may explain the absence 

 of records from North America. At present no information is 



' Loc. cit. p. 198, and Kulturversuche mil Kostpilzen, Bericht viii. (1899), 

 Jahrb, f. Wiss. Bot. , Bd. xxxiv. 1900, p. 347. 



VOL. XXVII. PART II. O 



