^^ A Monograph of the Erysiphaceae 



spicuous scars or the nearly black and decaying remains of the 

 old persistent mycelium) where the fungus grew in the previous 

 year. Eriksson remarks on the subject (119): "Die bei 

 diesem Pilze vorhandenen Perithecien scheinen iibrigens nicht fur 

 sich allein das Fortlcben des IVIehlthaues in dem Grade wie er dem 

 Gartner jetzt bckannt ist, geniigend zu erklaren, besonders wenn 

 man an die in den Gewachshausern so verheerende, so weil 

 bekannt nie perithecienfuhrende Form der Krankheit denkt. Ihre 

 dortige Lebenskraftigkeit muss unzweifelhaft auf andere Ueber- 

 winterungsweisen, z. B. auf ein unter giinstigen Umstanden in die 

 peripherischen Gewebe der Nahrpfianze eindringendes und da 

 fortlebendcs Mycelium, auf ein saprophytisches, hefepilzanhlichcs 

 Entwicklungsstadium des Pilzes im Sinne Brefeld's oder dgl. zu- 

 riickgefuhrt werden. Mikroskopische Beweise fQr die eine oder 

 andere Annahme sind jedoch noch nicli gebracht worden." 



In Europe S. pannosa is not uncommon, indeed in its Oidiiim- 

 stage it is very frequent, on wild and cultivated roses, although 

 pcrithecia are produced less commonly. From Asia (Cyprits) 

 Professor Gennardius has sent me specimens on Rosa damascena, 

 which are identical with European examples. Cooke (85) states 

 that in India roses suffer the attacks of 5. pannosa in the same 

 way as they do in Europe ; and in the same author's work on 

 Australian fungi (89) S. pannosa is recorded (an unsatisfactory 

 figure is given) "on rose-leaves" from Queensland. . 



How far these records and those of S. pannosa from the West 

 Indies and South America rest on the occurrence of an Oidium- 

 stage on rose-leaves, identified as that of 5. pannosa merely from 

 growing on this host-plant, it is impossible to say. The prevalent 

 practice of naming species oi t\x^ Erysiphaceae in the conidial stage 

 cannot be too strongly condemned, for it is not as a rule from reli- 

 ance on morphological characters that such naming takes place, 

 but simply from the assumption that the species of fungus which 

 occurs on a certain host-plant in one part of the world vtill be the 

 same as that growing on the same host in other parts. 



The danger of making such assumption is well seen in connec- 

 tion with a mildew common on American roses, which on account 

 of its occurrence on roses has been wrongly referred to the present 



species. 



pan 



