THE FUNGI WHICH CAUSE PLANT DISEASE 221 



mata; conidiophores wavy or zigzag, erect, simple, black, conidia 

 obovate, 1-septate, constricted, pale olivaceous, 20-24 x 9-10 ju. 



The conidial form is very common on various species of clover 

 in Europe and America while the ascosporic stage is mentioned 

 only by Cooke "" and Clevenger.'" 



P. cynodontis (Sacc.) Niess. on Cynodon, P. po» (Fcl.) Sacc. 

 on Poa and P. dapazioides (Desm.) Nke. on 

 Box and Rhododendron are European. 



P. makrospora Zimm. occurs on Durio zibel- 

 linus; 



P. sorghi V. Hoh. on Sorghum vulgare.'^^ 



Dothidella Spegazzini differs from Phyllachora 

 in having 2-celled hyaline spores, the cells un- 

 equal in size. There are over fifty species of 'una? ' Asci Ind 

 the genus. Epiphyllous, subrotund confluent, ^i^ter.^' ■*"^' 

 convex, grayish-black, on white spots; ostiole 

 granular; asci cylindric, short-stipitate, 60-70 x 8 /x; spores ob- 

 long, ovate oblong, hyaline, 10-15 x 5 /i. D. ulmi Duv.'^ Co- 

 nidia=Septoria ulmi and Piggatia astroidea. On elm in Europe 

 and America. Other species are D. thoracella (Rostr.) Sacc. on 

 Sediun, in Europe, D. betulina (Fries) Sacc. on Betula in Europe 

 and Asia. 



Sphseriales (p. 124) 



Mycelium chiefly confined to the substratum; perithecia vari- 

 able, usually globose, with a. more or less elongated ostiole, hairy 

 or smooth, free on the substratum, more or less deeply sunken, or 

 borne on or sunken in a stroma; asci borne basally, variable in 

 size, opening by a pore; spores variable, globose, ovate to elongate 

 or filiform, hyaline or colored; paraphyses usually present; conidial 

 forms various. 



The stromata may vary from a delicate hyphal weft to a firm 

 crustaceous structure. The pycnidia are mostly carbonous, black 

 and brittle. Conidia of many forms are present and often con- 

 stitute the only truly parasitic form of the fungus; the asci- 

 gerous form developing only after the death of the part of the 

 host involved. 



