183 



GRASSES OF IOWA. 



Fig. 83. Downy mildew of Hun- 

 garian grass Sclerospora aramini- 

 cola; oofif, O'^gonlum ; oo8, oosphere; 

 an, antherldlum ; oo, oospore. (Pam- 

 mel and Elns.) 



succumbed to the disease, the leaves 

 wilted and soon rotted. Later in 

 the season the leaves of older plants 

 being more rigid, did not show this 

 rotting, but many of the leaves of 

 the affected plants are brown and 

 torn up into fine shreds. A little 

 shaking will bring out a large num- 

 ber of small round bodies, the 

 oospores; these are enclosed in a 

 thick cell- wall. The spikes are 

 also frequently attacked, producing 

 large distortions. The pistil and 

 stamens do not develop, while the 

 bracts surrounding the essential 

 organs are greatly lengthened. 

 Thus in some affected spikes af Gol- 

 den "Wonder millet and Hungarian grass the distortions were 

 so large that they were not recognizable. The oospores are so 

 numerous as to fill up the tissue between the epidermal cells. 

 The oospores serve to cairy the fungus over winter. It is not 

 a difficult matter, if the seed is purchased from an infected dis- 

 trict, to carry the disease to remote distances, as it is a com- 

 paratively easy matter for some of the bracts containing 

 spores to get in with the seed, or for some of the spores to 

 become attached to the seeds. 



Mildew of Indian corn. — Iq a recent German scientific period- 

 ical, M. Raciborski describes a very destructive downy mildew 

 of corn which he has named Peronospora maydis. Many of the 

 fungi of this group cause great loss, as for example the potato 

 rot fungus, downy mildew of the grape, and others which 

 might be mentioned. This fungus of the corn is no exception 

 to the rule. It has been found but in one place in Java. No 

 doubt, however, it will spread and may yet become a source of 

 danger to us. The fact of its occurrence in Java is of interest, 

 because corn is not native there. The author looked for it on 

 native grasses, but failed to find any indications of its occur- 

 rence. 



Where did the fungus originate? Most • probably on some 

 other grass and from that spread to the corn. The descriptions 

 and figures suggest the similar European fungus on millet, 

 Sclerospora graminicola described above. In Java the fungus is 



