156 Journal of the Mitchell Society [February 



5. Aleurodiscus nivosus (B. & C.) H. & Litsch. 



Stereum acerimmi var nivosum B. & C. 

 Plates 16 and 31 



Plant forming crust-like elongated patches of definite outline, 

 about 1-23 mm. long by 1-4 mm. broad, the elongated axis vertical, 

 at first thin like a streak of whitewash, then thickening into a mat- 

 tress-like patch about 0.5-0.7 mm. thick with a free margin that is 

 black below; in age cracking across to make smaller areas as in 

 Stereum jrustulosum. Surface always chalk-white. Flesh brown be- 

 low a thin surface layer; hard, dry and rather friable. 



Spores (of No. 3897) white, oval, with a small, distinct mucro and 

 short, sharp, dehcate spines, 12.9-15.9 x 15.9-21.5[jl. A few spores 

 show a remarkable variation in having small blunt warts like a Hyd- 

 num. 



Very common, and to be found on almost every cedar tree. 

 Differs from A. candidus in more spiny spores, proportionately 

 narrower, longer and thinner fruiting bodies, and in growth on cedar. 

 Burt's description of the spores as smooth is incorrect for our speci- 

 mens. The close-set, slender spicules distinguish the plant at once. 

 Burt also describes the plant as thin with margin not free as in A. 

 candidus. This is true only for the young condition. As growth 

 continues the flesh becomes thicker and cracks across and the margin 

 becomes free and shows the blackish outer (under) side. 



3897. On bark of living cedar, December 14, 1919. 

 3920. On living cedar tree, December 22, 1919. 



6. Aleurodiscus acerinus (Pers.) H. & Litsch. 



A smaller and thinner species than the others treated ; crustaceous, 

 irregular to subcircular or rarely elongated, up to about 3 mm. wide 

 or when elongated up to a cm. long; chalk-white, minutely pulver- 

 ulent, the abrupt margin definitely outlined. Hymenium contain- 

 ing slender branched paraphyses that are much encrusted with crys- 

 tals. 



Basidia clavate, about half as large as in A. candidus, sterigmata 

 four, elongated. Spores (according to Burt) white, smooth, 6-7 X 

 10-12[JL. 



2020. On bark of living deciduous tree, December, 1915. We have misplaced 

 this collection which was seen and determined by Burt, and so have not 

 been able to make original observations on the spores. 

 Common on bark of trees. Curtis (as Stereum). 



