REVISIOX OF THE SCOTCH PERISPORIACEAE. U 



covering almost, theh' "whole surface, upon Spiraea 

 Ulmarial Alchemilla vulgaris I Taraxacum officinalel 

 and Hnmulus Lupulusl, to which last plant it is often 

 very destructive even in Scotland. Summer and 

 Autumn. 



Forth ! Clyde ! Tay ! Dee ! Moray ! Orkney ! 



Almost throughout Europe, in Siberia, and in North 

 America. 



3. S. Epilobii (Link) Sacc. {Scot Nat, 18S6, p. 

 220) (D. and R. Trail). —'Not scarce in summer and 

 autumn, upon Epilohium monfanurn and on E. parvi- 

 jiorum. 



Tay (near Montrose) ! Dee ! 



Central Europe. 



This species approaches very uear S. Castagnsl, from which 

 it differs chiefly in minor points— forming a denser mycelium, 

 l>earing erect sterile hyphae, as well as fertile ones, and also 

 having perithecia provided with radiating brown appendages. 



Genus 2. Podosphaera Kunze. 



Of this genns we have three forms in Scotland, viz., P. tri- 

 ■dactyla {Wallr.) = P. Kunzel Lev. (M.S. 1831), P. tnyrtillina 

 (Schub.) = P. Kunzel, var. mj/rflllina Kunze (M.S. 1831 var.), 

 and P. Oxyacanthne (DC.) = P. clandestina Lev. (M.S. 1832). 

 These three forms are very similar to one another, so much so 

 indeed that they are regarded by some mycologists as actually 

 belonging to a single species. But without seeking to dispute 

 the close relationship that exists between them, we may, in the 

 meantime at least, regard them as distinct, since they show 

 structural characters by which they may be recognised, besides 

 the distinction in their food-plants. P. trldacfyla and P. 

 viyrtlUina both have a poorly-developed mycelium (which may 

 readily be overlooked), but the perithecia are plentiful. The 

 Appendages of the latter in P. tridactyla on the top are few, 

 erect, and stiff, and the sporidia are about 20,a long ; while in 

 P. inyrtillina the appendages are rather more numerous, and 

 radiate outwards or bend downwards, and the sporidia are 2ofx. 

 to 30ya long. P. Oxyacanthae renders its attacks very evident 

 by covering all the young leaves and the tips of the twigs 

 with a grey mycelium, on which the perithecia are produced 

 only at rather a late season of th<' year, if at all ; and the 

 sporidia are slightly smaller than in P. tridactyla. 



4. P. tridactyla (Wallr.) D3 Bary.— On leaves of 

 Prunus Padus ! in the latter part of summer and in 



