246 ASCOMYCETES. 



Rh. symmetricum J. MiJller {Eh. mdumnale Schroeter)^ is a 

 form occurring on Salix purpurea and recently separated as a 

 distinct species. This willow, one of the best for cultivation, 

 may often be seen with its leaves covered with black spots, 

 and the disease may spread over every tree in a nursery. 



The apothecia are found on the upper surface of the leaf, 

 on black, shining, and much wrinkled cushions. In addition, 

 black apothecial cushions are developed on the under surface 

 of the leaf, which is not the case with any other species of 

 Rhytisma. According to Schroeter, the spores ripen in autumn 

 on still living leaves. 



(This species may be synonymous with Rh. australe Dur. et Mont, on 

 Salix purpurea in Algeria.) 



A species which causes little thick cushions on Salix Caprea has been 

 called Rhytisma umhonatum Hoppe. 



Rh. andromedae Pers. occurs on leaves of Andromeda polifolia. (Britain 

 and U.S. America). 



Rh. empetri Fries, on leaves of Empetrum nigrum. (Britain). 



Rh. juncicolum Eehm on Junxrus Hostii. 



Rh. urticae Fr. on stems of Urtica dioica. (Britain and U.S. America). 



Rh. bistortae D. C. on Polygonum viviparum in France, Greenland, and 

 America. 



PSEUDOPHACIDIEAE. 



The apothecia are at first embedded in their substratum, 

 under the superincumbent layers of the host-tissue, and form 

 blistered patches ; on rupture, this cover forms a rim round 

 the apothecial cushion; the excipula of the apothecia themselves 

 are membranous, generally black, and dehisce by lobes or 

 fissures on the apex. 



Cryptomyces. 



The apothecia break out from the substratum as black crusts. 

 The asci contain eight oval, unicellular, colourless spores. The 

 paraphyses are thread-like and septate. 



Cryptomyces maximus Fries.^ (Britain and United States). 

 This fungus lives parasitic on twigs of various species of willow 



^J. Miiller, "Zur Kenntniss d. Runzelsohorfs," Pringsheim's Jahrittch, 1893. 

 Schroeter, Flora v. Scldesien, 1894. 



Both appear to be identical with Rh. amphigenum Wallr. (Flor. Crypt, ii. 412). 

 ^ Tulasne, Select, fangorum Carpologia, iii. 



