THE FUNGI WHICH CAUSE PLANT DISEASE 519 



In part=Mycosph£erella, Leptosphcpria. 



The genus is a very large one similar to Phoma and Phyllosticta 

 except in its spore form and in the ostiole which is frequently 

 very large. Septoria and Phleospora are distinguished only by 

 the lesser development of the walls of the latter and many species 

 which in early stages pass as Phleospora would in older stages be 

 classed as Septoria. 



Septoria and Rhabdospora are distinguished only by the part 

 of the host affected, stem or leaf, and many forms in these two 

 genera are undoubtedly identical. 



S. pisi West, is on peas. 



S. piricola Desm. on pear and apple = My cosphserella sentina. 

 See p. 246. 



S. populi Desm. on Populus= My cosphserella populi. See p. 250. 



S. phlogis Sacc. & Speg. on Phlox =Leptosphaeria phlogis. See 

 p. 258. 



S. ribis Desm."^ 



Hypophyllous; spots small, irregular, bounded by the leaf veins, 

 brownish-purple; pycnidia in- 

 nate, minute, convex, brownish- 

 black; cirri in mass reddish; co- 

 nidia elongate, linear, curved, 

 50 M long. 



On gooseberry and currant, 

 causing leaf spots and defolia- 

 tion. 



S. aciculosa E. & E. 



Pycnidia innate to superficial, 

 grouped, minute, amphigenous; conidia needle-shaped, continuous, 

 15-20 X 0.75 IX. 



It is found on the strawberry. 



S. fragariae Desm. 



Epiphyllous; spots suborbicular, brown, with reddish-brown 

 margin; pycnidia minute, innate, prominent, brownish; cirri white; 

 conidia cylindric, obtuse, 3-septate. 



Perhaps =Mycosphaerella fragarise. See p. 244. 



On strawberry, cultivated and wild, forming circular leaf 

 spots. 



Fig. 359. — S. libis, a pycnidium aud 

 spores. After Longyear. 



