100 
IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
these. The writer propagated from them and although the cuttings were 
far removed from the galls the characteristic enlargements appear oc- 
casionally on plants of the species even after several asexual generations. 
Not observed on other hosts when grown in Alaska. 
Peronosporaceae 
Peronospora ohovata Bon. On Spergula arvensis. A common parasite. 
Peronospora parasitica (Pers.) DeBy. On Arahis hirsuta. Collected 
in the basin back of Juneau. Does not appear to be common or widely 
distributed. 
Plasma para epilobii (Raf.) Schroet. On Chamaenerion latifoUum. 
Common. 
Erysiphaceae 
Brysiphe cichoracearum DC. On Artemisia elatior, Solidago sp., Chrys- 
anthemum hortorum. Quite common at Skagway on Artemisia and at 
Haines on Solidago. 
Brysiphe graminis DC. ? On Agrostis exarata. Common in the conidi- 
al stage but perithecia not observed. 
Brysiphe polygoni DC. On Aquilegia formosa, Geum macrophyllum, 
Lathyrus ma^itima. Common at Haines and Skagway. 
Micros phaera alni (Wallr.) Wint. Collected at Sitka and Skagway on 
Alnus sitchensis. 
Sphaerotheca humuli (DC.) Burr. On Bpilobium alandulosum, Fragaria 
hybrids, Ribes bracteosum, Rubus spectabilis. A very common species 
especially on the first and fourth hosts. 
Sphaerotheca humuli fuliginea (Schlecht.) Salmon. On Arnica latifolia. 
Collected at Skagway. 
Sphaerotheca mors-uvae (Schw.) B. & C. On Ribes lacustre, Ribes 
grossularia, Ribes vulgare. Common and generally destructive on the 
first two hosts. Ribes vulgare is generally quite immune but some varieties 
are affected to a limited extent. 
Sphaerotheca pannosa (Wallr.) Lev. On Rosa spp. Varieties of culti- 
vated roses belonging to several types are susceptible, especially in the 
greenhouse. 
Sphaerotheca sp. On Chamomilla sauveolens at Skagway. 
Uncinula salicis (DC.) Wint. On Populus trichocarpa, Salix sitchensis, 
Salix sp. (native). 
Sphaeriaceae 
Ceriospora ribis P. Henn. & Plo. On stems of Ribes bracteosum. 
Cucurbitaria conglobata (Fr.) Ces. On dead stems of Alnus sitchensis. 
Diaporthe calosphaeroides E. & E. On stems of Sambucus pubens. 
Diaporthe concrescens (Schw.) Cke. On stems of Ribes sp. (goose- 
berry). 
Diaporthe marginalis Pk. On stems of Alnus sitchensis. 
Diaporthe salicella Fr. On stems of Salix sp. (cult.). 
Didymella eupyrea (Sacc.) Michel. On old overwintered stems of 
Urtica lyallii. 
Didymosphaeria sp. On leaves and stems of Blaeagniis angustifolia. 
Leptosphaeria coniothyrium (Fckl.) Sacc. On dead stems of Ribes 
nigrum. 
