MELAMPSORA. 367 



The patches of Caeoma laricis Hartig.^ appear as golden-yellow 

 cushions on the underside of the needles. The sporophores from 

 which the aecidiospores are abjointed, form the centre of the patch, 

 the periphery being occupied by numerous sterUe threads, which 

 grow out as long paraphyses ; it may so happen that the whole 

 cushion consists only of these last. The formation of Gaeoma- 

 patches is preceded by that of little pycnidia (spermogonia), 

 which break out from under the cuticle. The mycelium lives 

 intercellularly, and dies after the shedding of the Caeoma- 

 spores. 



Melampsora betulina (Pers.) (Britain and U.S. America). 

 Uredo- and teleutospores occur on the leaves of the birch 

 {Betula alba). Plowright^ found from arti- 

 ficial infection that this species produced 

 Caeoma laricis on the needles of Larix 

 europea. A second form of Caeoma laricis 

 was obtained by Hartig, both from infec- 

 tion by Mel. tremulae Tul. from the aspen, 

 and by Mel. populina Jacq. from the black 



poplar. Pio. 199. _ Melampsora 



M. populina (Jacq.)« (Britain and U.S. ^rirspore.fo™^ (Afte? 

 America). Uredo- and teleutospores found ^uiasne.) 

 on Populus nigra and P. ialsamifera. 



M. populina and M. tremulae are probably identical, for Hartig 

 has found the same Melampsora on black and balsam poplars 

 as on aspen, and in each case he produced Caeoma laricis by 

 means of the uredospores. Schroeter states that the Melampsora 

 of Populus nigra produces Caeoma allii of Allium. 



M. aecidioides D. C. (Britain). Uredo- and teleutospores on 

 leaves of silver poplar (P. alba and P. canescens). Plow- 

 right connects with it a caeoma-form on Mercurialis {Caeoma 

 merourialis). Schroeter states that the Melampsora of Populus 

 tremula produces Caeoma mercurialis. 



The Melampsorae of Willows were until recently grouped 

 under a collective name, M. salicina ; several species are now 

 recognized, others require verification. 



^ R. Hartig, Wichtige Krankheiten d. Wcddbdumen, PI. V. 



^ Plowright (loc. cit. ). 



'E. Hartig, Baton. Centralblatt, XLvr., 1891; " The leaf-rust of cottonwoods," 

 U.S. Dept. of Agriculture Bepwt, 1888, p. 390. 



