506 THE FUNGI WHICH CAUSE PLANT DISEASE I 



Ascochyta Libert (p. 505) 



Usually producing definite spots; pycnidia gloljose-lenticular, 

 ostiolate; conidia ovate. , 



About two hundred fifty species. 



A. pisi Lib."' 9»' 92=Mycosphfflrella pinodes.*^' See p. 250. 



Spots variable in size, roundish, yellowish with brown margin; 



pycnidia centrally located, black, of angular cells, 5-7 fi; ostiole 



rounded,* surface reddish brown; conidia 



slightly constricted at the septum, oblong, 



12-16 X 4-6 m; exuded spore-mass brown. 



On peas, beans, vetch, Cercis, etc. The 

 pycnidia are visible on the dead areas of the 

 stems, leaves, pods or seetls. The mycelium 

 hibernates in affected seeds, reduces their 

 germinating power and. carries the fungus 

 over to the succeeding crop. 

 Fig. 350.— a. citri, ^' boltshauseri Sacc. on bean in Swit- 

 cMdo^" ■"^^'^ ^^' zerland'* is closely related to- the last 



species. 

 A. armoracise Fcl. is on horse radish, causing leaf spots; 

 A. ellisii Thiim. on grape; 



A. brassicae Thum. on cabbage, forming large dull patches; 

 often quite injurious. 

 A. rhei E. & E. 



Spores finally constricted and 1-septate, 7-12 x 3.5-4 n, hyaline. 

 On rhubarb. 

 A. viciae Lib. 



Epiphyllous; spots roundish, reddish, margin elevated, orange 

 red; pycnidia minute, clustered, black, 90-100 n; conidia 

 oblong-ovate, obtuse, slightly constricted, 12-15 x 4-5 n; exuded 

 mass white. On Vicia. 

 A. nicotianae Pass.'* 



Spots between the veins, irregularly scattered, brown; conidia 

 oblong ovate, constricted at the septum. On tobacco. 

 A. parasitica Faut. 



Spots whitish; epiphyllous; pycnidia small, black. Conidia el- 

 liptic, 3-i X 6-10 li. 



