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 sterile threads, which 

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

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

 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 

 {Bdula nlha). 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. tremnlac Tul. from the aspen, 

 and by Md. popi(Mna Jacq. from the black 

 poplar. 



M. populina (Jacq.)=^ (Britain and U.S. ur"dospore-sorus. (After 

 America). Uredo- and teleutospores found Tuiasne.) 

 on Fop V his nigra and P. halsamifera. 



M. pojndina and M. tremulae are probably identical, for Plartig 

 has found the same Mclainiysora 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 Melampsoia 

 of Popuhis 7ii{/ra produces Caeoma allii of Allium. 



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

 leaves of silver poplar {P. alha and P. canescens). Plow- 

 right connects witli it a caeoma-iorni on Mercurialis {Caeoma 

 mercurialis). Schroeter states that the Melampsora of Popidus 

 tremulct 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, Wichtif/e Krankheiten d. WaJdbanmtn, PI. V. 



2Plownght(/oc. cit.). 



•'R. Hartig, Botan. Centralhlatt, XLVi., 1891; " The leaf-rust of cottomvoods, " 

 U.S. Dtpt. of Af/ncnlture Beport, 1888, p. 390. 



Fig. 199. — Melnmpsori' 

 Oi tulina. Portion of n 



