82 Wisconsin Academy of Sciences, Arts, and Letters. 



one can hardly decide that on morphological grounds without an 

 abundance of material. 1 find this in Wisconsin only to the 

 north and with few pycnidia. Much the best specimens that I 

 have seen were collected at North Yakima, Wash. (Wis. Acad. 

 Sci. Arts & Lett. Z5:778). 



In Farlow's Host Index, Populus balsamifera is given as a 

 host of Septoria salicina Pk. I presume that this refers to what 

 I have called group 1. This form looks quite distinct but it 

 merges into group 2 and that again into group 3 in a way that 

 makes it difficult to draw a line of separation, while the charac- 

 ters of the sporules are identical. Septoria salicina Pk. differs in 

 its uniseptate sporules. Of Septoria populi Desm., which has 

 nniseptate sporules, I have seen no American specimens. Fungi 

 Columbiani 2873, issued under this name seems to be the same 

 as 2872 which is labeled Septoria musiva Pk. On neither have 

 I found a Septoria. I may mention that F. Col. 1587 on Populus 

 tremuloides collected by J. B. Ellis at Newfield, N. J. and issued 

 as S. musiva Pk. bears Marssonina rhabdospora (E. & E.) Magn. 

 at least in the two copies which I have seen. F. Col. 3486 on 

 Populus balsamifera collected at St. Johnsbury, Vt. by W. P. 

 Carr and issued as Septoria populi Desm. is of the form with 

 black bordered alutaceous spots that I have placed in group 2. 

 Pacific Slope Fungi 1723 on Populus Fremonti collected in Cali- 

 fornia by Copeland and issued by Baker as Septoria popidi Desm. 

 is somewhat intermediate between groups 2 and 3. Fungi Col- 

 umbiani 1257 on Populus angustifolia collected at Golden, Colo- 

 rado, by Bethel, and issued as Septoria populi Desm. has subcir- 

 cular spots of a yellowish white or sordid white color with an ir- 

 regular grey-brown border 2-A mm. in diameter ; the pycnidia are 

 hypophyllous, broad and collapsing ; the sporules continuous 23- 

 35 x 31/2-4^. While this does not correspond with S. populi 

 Desm. it is different from any Septoria on Populus that I have 

 seen and judging from the single specimen may prove to be dis- 

 tinct. Cylindrosporium oculatum Ell. & Evht. on Populus del- 

 ioides (Put-in-Bay, Ohio) has hemispheric-superficial pycnidia 

 and obtuse sporules 30-50 x 3/x becoming 3 or more septate. This 

 forms circular grey to sordid spots about V2 cm - in diameter with 

 a narrow dark border. I would include it in Septoria musiva Pk. 

 as representing forms 1 and 2 on Popxdus deltoides. Specimens 



