14 Bulletin 313 



PsEUDOPERONospoRA cuBENSis (B. C.) Rostcvv. — Attacks leaves 

 of cucumbers, cantaloupe aiid other members of the family Cucurbi- 

 tacese. Causes indefinite, yellow spots which frequently unite ; leaf 

 dies, blackens and shrivels. Conidiophores arise from the stomata 

 of the lower surface and sometimes from the uooer surface. 

 180-400 X 5-9 /x, 3-4, sometimes 2-5 times branched, forming acute 

 angle; conidia gray or brownish, ovoid to ellipsoid, papillate, 

 20-40 X 14-25 IX. 



41. Infected leaf of cucumber. 42. Conidiophores and conidia, 1/12. 



Bremia lactuc^ Reg. — On the leaves of lettuce and other Com- 

 positise. Causes a wilting and dying of the leaves. Conidiophores 

 most common on under surface of leaves but sometimes on the up- 

 per surface, single, nimierous, nmch branched, each tip bearing a 

 disk with four tips for the spores. Conidia ovate, 16-22 x 15-20 /a. 



43. Conidiophores and conidia. 1/12. 



