FUNGI IMPERFECT! 



363 



Septoria Ribis Desm. 1 is common upon various species of Ribes. 

 \Yith respect to the economic hosts many varieties of both currants 

 and gooseberries are subject to attack. Large spots with pale 

 centers and brown borders are produced (Fig. 181). These are 

 readily distinguished from those produced by the anthracnose (cf. 

 Fig. 79) by the large size, the well-defined outline, and the pale 

 central dead area. The pycnidia are found in small groups at the 

 centers of the older spots. 

 They are subspherical, and, 

 when approaching maturity, 

 crowded with spores arising 

 from short filiform conidio- 

 phores. The conidia are long- 

 filiform and measure 50-60 x 



3-4 A*. 



Septoria Rubi West pro- 

 duces numerous small spots, 

 usually pale in the centers with 

 colored borders, on the leaves 

 of various species of Rubus, 

 both blackberries and rasp- 

 berries. 2 The fungus has been 

 reported from many sections 

 of the world, and is doubtless very generally distributed. Pyc- 

 nidia are developed in the center of the larger spots, and these 

 give rise to long tapering spores, 40-50^, ordinarily twice or 

 more septate by rather indistinct divisions. 



Septoria consimilis E. & M. The lettuce leaf spot, caused by 

 this fungus, is prevalent on garden lettuce, particularly during the 

 latter part of the season. It is perhaps the chief " spot " fungus 

 .of this plant, but may be held in check by the immediate destruc- 

 tion of the discarded and seeded plants in the field at the close of 

 the season. 



Septoria Dianthi Desm. produces small brown spots upon the 

 leaves and internodes of the carnation. The leaves are often bent 



1 Pummel, 1 ,. II. Spot Diseases of Currants and Gooseberries. Iowa A-l. l.\]>. 

 Sta. Built. 13: 67-70. Ji--s. 15-16. iSyi. 



2 Ohio Agl. Exp. Sta. Built. 4 (6) : 126. 1891. 



FIG. 181. LEAF SPOT OF CURRANTS 

 (Photograph by F. C. Stewart) 



