230 ASCOMYCETES. 



Diachora onobrychidis (D. C.).^ This fungus is common 

 on sainfoin {Ondbrychis sativa) and Lathyrus tuberosus, causing 

 black spots on both surfaces of the leaf. During summer 

 pycnidia arise on the spots, and from them are produced spindle- 

 shaped conidia (spermatia) with tail-like appendages. Later 

 there arise spherical perithecia containing asci arranged in tufts 

 on the walls. The asci contain eight oval, hyaline, unicellular 

 spores. 



Dothidella. 



The perithecia are black and embedded Ln the stroma, 

 similarly to Phyllachora. The pale-coloured spores are, how- 

 ever, two-celled. 



Dothidella betulina (Fries.). (Britain and U.S. America.) 

 The black stromata form spots on the upper surface of 

 birch leaves. In these the perithecia arise, and reach maturity 

 in spring. The asci contain eight elliptical greenish spores, 

 consisting of two unequal cells with rounded-off ends. 



D. ulmi (Duv.). (Britain and U.S. America.) A species 

 siinilar to the preceding, and causing round blistered spots 

 of a grey colour on the upper surface of elm leaves. Pycnidia 

 {Piggotia astroidea) are formed in summer, perithecia in the 

 following spring. 



Dothidea. 



The stromata have the form of black projecting cushions, 

 in which numerous perithecia are embedded. The asci contain 

 eight greyish or brown spores, consisting of two cells with a 

 constriction between them. 



Dothidea virgTaltomm (Fries.) attacks living branches and 

 stems of birch, and develops further on the dead parts. The 

 stromata originate in the wood, then breaking through the 

 bark, make their appearance externally as large black cushions. 

 Whole stems may be covered by these cushions. 



D. sphaeroidea (Cke.) occurs on living needles of juniper. 



Plowrightia. 



The stromata are black, and run together in masses. The 

 asci are eight-spored ; the ascospores ovoid or oblong, hyaline 

 or light yellow, and two-celled. 



'J. MuUer, Pringsheim's Jahrbtick, 1S93. 



