EHYTISMA. 71 



On living leaves of Acer pseudoplatanus and A. campestre ; 

 also on other species of Acer in other countries. 



The black patches appear on the leaves during summer, 

 and in the autumn spermatia are developed in those same 

 conceptacles that become ascophores and contain asci the 

 following spring, when the leaf is partly decayed and has 

 been lying on the ground throughout the winter. 



Specimen in Kew Herbarium, named by Persoon, examined, 

 also specimen in Fries' Scler. Suec, n. 207. 



Rhytisma punctatum. Fr., Vet. Akad. Handl., 1819, 

 p. 104; Cke., Hdbk., p. 756; Eehm, Krypt. -Flora, Disc, 

 p. 83; Sacc, Syll, viii., n. 3084. (figs. 1-3, p. 91.) 



Ascophores gregarious on a roundish, yellow spot on the 

 leaf 1-1 • 5 cm. across, crowded, rarely more or less confluent, 

 black, circular or elongated and often curved, 1-1^ mm. 

 across ; excipulum parenchymatous, cells minute, olive ; at 

 length splitting lengthwise or in a radiate manner, and 

 exposing the greyish disc; asci clavate, apex narrowed, 

 8-spored; spores needle-shaped, apex blunt, base pointed, 

 straight, continuous, guttulate, hyaline, arranged in a 

 straight, parallel fascicle, 35-40 x 1*5-2 ;* ; paiaphyses 

 slender, colourless, about 1 jx, thick. 



Xyloma punctatum, Pers., Syn. Meth. Fung., p. 104. 



Spermogonia. Spermatia cylindrical, straight, hyaline, 

 5-6 X 1 • 5 /i. 



On living leaves oi Acer campestre smd Acer pseudoplatanus ; 

 also on other species of Acer in other countries. 



The spermatia are formed during the autumn, the asci 

 appearing in the same cavities the following spring on the 

 dead leaves. 



Eeadily distinguished by the stroma being broken up into 

 numerous minute portions, crowded together on a yellowish 

 patch. 



Specimens examined : Eehm, Ascom., 366 (ascigerous 

 form) ; Sydow, Myc. March., n. 351 (Spermogonia). 



Rhytisma salicinum. Fr., Vet. Akad. Handl., 1819, 

 p. 104; Cke., Hdbk., p. 755, fig. 357; Eehm, Erypt.-Flora, 

 -Disc, p. 84, figs. 1-7, p. 65; Sacc, Syll., viii. n. 3085. 



Stroma forming circular or irregular thiokish, shining 



