S Bulletin 313 



Albugo Candida (Pers.) Kuntze. — On radish, turnip, shepherd's 

 purse and many other species of Cruciferese. Causes white or oc- 

 casionally light yellow blisters (sori) on all parts of the host above 

 ground. Frequently causing pronounced hypertrophies. Conidia- 

 phores hyaline clavate, about 35-40 x 15-17 /x; conidia globular, hya- 

 line, thin walls. 15-18 ;a. 



20. Infected stem of Capsella bursa-pastoris. 21 Infected leaf of turnip. 

 22. Conidiophores, 1/12. 23. Conidia, 1/12. 24. Mature oospore, 1/12. 



Albugo ipomoeae-panduran^ (Schw.) Swing. — On stems, 

 leaves, and sometimes petioles of the sweet potato, Ipomcca pandu- 

 ratcc, I. hederacea (seedling) and other species of Convolvulaca?. 

 Causes white, or light yellow blister-like spots and sometimes very 

 pronounced enlargements and distortions of the stems. Spots are 

 usually circular, sometimes confluent and 0.5-20 mm. Conidio- 

 phores, hyaline, clavate, unequally curved at base, 15-30 /a; Conidia 

 hyaline, nearly spherical, slightly cylindrical, 14-20 x 12-18 fx. 



25. Conidiophores and Conidia, 1/12. 



Albugo portulac^: (D. C.) Kuntze.^On all parts of Porhdaca 

 oleracea above ground. Causes white to yellowish circular or slight- 

 ly irregular spots ranging to 5 mm. in diameter. Conidiophores 

 hyaline, clavate about 9 x 25 /x. Conidia varying from spherical at 

 base to cylindrical at tip of chain, walls hyaline, contents light yel- 

 low, about 12-15 X 15-22 fx. 



26. Infected leaf of Portulaca oleracea. 27. Conidiophores and Conidia, 

 1/12. 



Albugo tragopogonis (D. C.) S. F. Gray.— On salsify and many 

 other Compositse hosts. On the stems and under-side of leaves. 

 Sori prominent, deep-seated, white or yellowish, circular or elong- 

 ated, 1-8x1-3 mm. Conidiophores, clavate, hyaline, 40-50x12-15 

 /i, ; Conidia, short-cylindric, the terminal larger and less angular than 

 the lower, membrane with equatorial thickening, hyaline or light yel- 

 low, 18-22x12-15/.. 



28. Conidium, 1/12. 29. Oospore, 1/12. 



