USTILAGO. 287 



ated best at 10" C, and not so well above IS^'C. This 

 conclusion is supported by experiments of Kellermann and 

 Swingle. Xeither these investigators nor Jensen, however, agree 



'^, 



Fio. 157. — Ustilago perennans on Arrhenatherum elating (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 phut.) 



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 whicli 

 tliey distinguish as Vst. avenue 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. 



