26 Bulletin 313 



Penicillium luteum Zuk. — On the roots of the sweet potato. 

 Causes a rot. Produces abundant lemon-yellow mycelium through 

 the potato; conidiophores floccose and spreading, 20-100 /x (mostly 

 30-60 by 3 fi) ; conidia elliptical or fusiform, greenish, 2.4 x 2.3 fi; 

 perithecia smooth, brown and finally brick-red. Asci small, numer- 

 ous, globular to ovate and containing 8 spores. Spores, ovate to 

 ovate-oblong and ridged, at first hyaline, becoming light brown. 

 All attempts to germinate these spores failed. 



92. Germinating conidia, conidiophore and spores in hanging drop culture, 

 1/6. 93. Germinating spores, 1/6. 94. Perithecium, 2/3". 95. Asci and asco- 

 spores, 1/12. 



Erysiphe cichoracearum D. C. (= Oidium ambrosice Thiim, 

 page 116). — On green parts of a number of plants. Causes 

 whitish, sometimes pinkish, downy growth which is usually evanes- 

 cent. Conidia small, white, elliptic, 4-5 x 7-5.3 /jl. Perithecia 

 grouped or scattered and 80-140, sometimes 180 fx, in diameter. 

 Appendages brown and variable in number and size. Asci 4 to 36, 

 usually 10-15, and variable in size and shape, ovate or subcylindrical 

 to broadly ovate stalked, 58-90 x 30-35 /jl. Ascospores 2, occasion- 

 ally 3, 20-28 X 12-30 /.. 



96. Perithecium, 1/6. 97. Asci, 1/12. 98. Ascospores, 1/12. 



Erysiphe graminis D. C. (== Oidium monilioides Lk., page 

 116). — On the leaves and sometimes on other parts of wheat, bar- 

 ley and other cereals. Causes white, grayish or brownish, moldy 

 patches on affected parts. Conidia ovoid, whitish, 25-30 x 8-10 /x. 

 Perithecia 135-280 fx., usually about 200 w, scattered or grouped. 

 Asci 9-30, cylindric or ovate-long, more or less pedicilate, 70-180 x 

 25-40 fi. Spores 8, occasionally 4, 20-23 x 10-13 fi, and seldom 

 maturing on living host. 



99. Conidiophore and conidia, 1/12. 100. Immature ascus. 



