478 IOWA ACADEMY OF SCIENCE 



young hybrid seedlings of this species and the garden black 

 currant (B. nigrum) became severely infected during the 

 fall of 1915. It has not been observed on B. nigrum. 



On Bibes rubnum L. (190). Does not seem to be severe on 

 this host and there seems to be a great deal of difference 

 in the resistance of the different varieties. Of the red cur- 

 rants grown at the Station, Perfection seems to be most 

 susceptible. 



On Bubus speetabilis Pnrsh. (187). Infection seems to be 

 severe, but local. 



Spaerotheca mors-uvae (Schw.) B. & C. Gooseberry mildew, 

 this can be distinguished from the preceding by its dark, 

 dense, felted mycelium. It is abundant on the fruits while 

 S. liumuli is mostly confined to the leaves, petioles and young 

 stems. 



On Bibes lacustre (Pers.) Poir. (74). During 1914 this 

 species was very abundant and destructive, being found 

 on berries, leaves and stems. Scarcely a fruit escaped its 

 ravages. During 1915 it did but little damage. Two thor- 

 ough sprayings with Bordeaux mixture helped to keep it 

 in check. The host is native to Alaska, but ddes not occur 

 near Sitka. 



On Bibes uva-erispa L. (75). Very abundant and destructive 

 on some varieties of the English gooseberry, while other 

 varieties (e. g. "Whitesmith) seem nearly immune. 



Sphaerotheca pannosa (Wallr.) Lev. Rose mildew. 



On Bosa sp. (180). This mildew is common and troublesome 

 on many of the tea roses grown indoors. 



Erijsiphc graminis DC. Grass mildew. This species is not 

 abundant, but the conidial stage occurs sparingly on a few 

 grasses. 



On Agrostis exarata Trin. (191). 



Erysiphe sp. The conidial stage of a mildew has been collected 

 on Achillea borealis Bong., and on Banunculus sp. The for- 

 mer may be E. dehor aeearum, DC., while the latter probably 

 is E. polygoni DC. 



Microsphacra alni (Wallr.) Wint, Alder mildew. This species 

 does not seem to be common. 



