USTILAGO. 



287 



ated best at 10" C, and not so well above 15° C. This 

 conclusion is supported by experiments of Kellermann and 

 Swingle. Neither these investigators nor Jensen, however, agree 





Fig. 157. — Ustitago perentians on Arrhenaiherum elaiius (Oat grass). The grains 

 are transformed into black smut-masses ; the appearance of the infected spikelets 

 is quite distinct from that of the healthy one to the right, (v. Tubeuf phot.) 



with Brefeld's view, that the fungus is introduced into fields 

 with fresh farmyard manure. 



Kellermann and Swingle have found a smut on oats in America whieli 

 they distinguish as Ust avenae var. levis. 



Ust. KoUeri Wille. This is another species of oat-smut recently dis- 

 tinguished ; it has smooth spores, and is said to cause even greater damage 

 than Ust. avenae. 



