286 DISEASES OF CULTIVATED PLANTS 



the centre; asci normally 8-spored, often fewer; spores 

 elongated, hyaline, i -septate. 



Sneezewort leaf spot. Minute black spots are formed on 

 the living leaves of Achillea ptarmica by Schizothyrum ptar- 

 micae (Desm.). The spots are circular or elliptical, and expose 

 the disc by an elongated or stellately radiating slit. The asci 

 normally contain eight spores, but frequently not more than 

 two are present. Spores elliptic-oblong or very slightly 

 clavate, hyaline, i-septate, 10-14x5-6 //.; paraphyses slender, 

 branched. 



In the spermogonia or conidial form the perithecia are 

 flattened; spores ovate-oblong, hyaline, iox6-7/u. 



B. Spores coloured. 



BULGARIA (FRIES.) 



Ascophore more or less gelatinous, erumpent, the blackish 

 disc gradually expanding until plane ; asci 4-8-spored ; spores 

 elongated, continuous, brown. 



Distinguished by the large, black, fleshy-gelatinous asco- 

 phore. 



Beech bark fungus (Bulgaria polymorpha, Wetts.) is very 

 common in this country as a saprophyte on dead trunks of 

 beech and oak. It is at times a true parasite on the bark of 

 the same trees. Ludwig considers the Bulgaria as a 

 dangerous parasite to the oak. Biffen, who has made a 

 special study of this fungus, finds that the results of its action 

 on oak wood are to dissolve and probably decompose the 

 lignin, and to dissolve the pectates of the middle lamella. 

 No further action was observed, either in pure cultures or in 

 naturally diseased wood, pointing to further action. 



Ascophores gregarious, bursting through the bark as scurfy 

 brown knobs about the size of a pea. The disc gradually 

 expands until it becomes almost plane, with more or less of a 

 raised margin, 1-3 cm. across, pitch-black, shining, cutting 

 like a piece of indiarubber. Spores sometimes only 4 in an 

 ascus, and then brown. Sometimes there are 8 spores in an 

 ascus, four brown and four somewhat smaller and colourless, 

 10-14X5-6 //. Biffen states that the colourless spores 



