IOWA ACADEMY OF SCIENCES. 145 



destroying large numbers of young plants of Setaria 

 viridis. In whole patches it prevented the maturing 

 of seeds. 

 Plasmopara Viticola (B. and C.) B. and DeT. 



Abundant. Destructive to cultivated grape (Vitis Labrus- 

 ca), affecting leaf, stem and fruit. Also affecting the 

 growing of young shoots of Vitis riparia, in some 

 cases killing the young shoots. 

 P. Halstedii (Farlow) B. and DeT. 



Not common, on Helianthus annuus, H. tuberosus, Silphium 

 laciniatum, Xanthium Canadense, Centaurea. 

 Bremia Lactucce Kegel. 



Not observed although abundant in 1893. 

 Peronosiwsa Vici<x (Berk.) DeBy. 



Abundant in latter part of May and early June on Vicia 

 Americana. 

 P. Arthuri Farlow. 



Abundant on Oenothera biennis. 

 P. parasitica (Pers.) DeBy. 



Abundant on leaves and stems of Lepidium intermedia, 

 L. Virginicum, killing the affected plants. On leaves 

 of Capsella bursa pastoris not destructive. Brassica 

 nigra, B. campestris, Raphanus sativa, Draba Carolin- 

 iana. Sisymbrium officinale seriously affected. 

 P. Potentilke DeBy. 



Not found in 1895. Local in 1891. 

 P. effusa (Grev) Rabenh. 



Abundant on Chenopodium album in May and June. 

 P. EuphorMoi Fuck. 



Locally abundant on Euphorbia Preslii and E. maculuta. 

 P. alta Fuckel. 



Abundant on Plantago major. 



PERISPORIACEAE. 

 Podosphcera OxT/acanthce (D. C.) De By. 



Abundant on cultivated (Prunus Cerasus) and P. pumila. 

 Not common on P. Americana; also observed on young 

 shoots of Crataegos punctata, and C. mollis; July, 

 August and September. 

 Spcerotheca Mali (Duby) Burrill. 



Common on suckers of Pyrus Mains and young shoots of 

 P. toringo in nursery, June, July and early August. 

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