A NEW LEAF-SPOT DISEASE OF 

 POLYGONUM PERSICARIA 



P. J. O'Gara 

 (With Plate io) 



In July of 1914 and August of 1916, Mr. W. W. Jones, bot- 

 anist in the department of agricultural investigations, American 

 Smelting & Refining Company, made collections of Polygonum 

 persicaria L. showing an apparently new leaf-spot. An examina- 

 tion of the literature indicates that this leaf-spot disease has not 

 been previously noted and that the organism is an undescribed 

 species of Septoria quite different from the species of Septoria 

 described as occurring upon Polygonum or related genera. From 

 field observations it would seem that this type of leaf-spot is 

 rather rare, only two small collections having been made as noted 

 above. The description of the species is as follows : 



Septoria persicariae sp. nov. 



Maculis amphigenis subeircularibus, 1-8 mm. diam., sparsis v. 

 saepe confluentibus, rubiginoso-brunneis dein centro griseo-brun- 

 neis v. griseis, anguste purpureo v. violaceo-limbatis ; pycnidiis 

 amphigenis, parcis v. numerosis, sparsis v. aggregatis, immersis, 

 membranaceis, brunneis v. atro-brunneis, globosis 50-120^ diam., 

 osteolo depressis v. parvulo pertusis ; sporulis hyalinis filiformi- 

 bus utrinque obtusis v. attenuatis v. saepe uno apice latoribus 

 altero gradatim attenuatis (sub-clavulatis) , rectis, curvis v. saepe 

 flexuosis, continuis v. indistincte pluriseptatis, saepe minute gut- 

 tulatis, 17-60 X 1-3 cirrose expulsis ; basidiis non vivis. 



Hab. in foliis vivis Polygoni persicariae, Salt Lake Valley, 

 Utah, Amer. Bor. (Wyatt W. Jones). 



Department of Agricultural Investigations, 

 American Smelting & Refining Company, 

 Salt Lake City, Utah 



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