4 USTILAGO AVENAE AND USTILAGO LEVIS 



Jensen proved, by infection experiments, that each suscept — oats, wheat, 

 and barley — had its respective and specific loose-smut pathogene. To 

 the smut fungi on oats he finally gave the name TJstilago a venae. He did 

 not, however, at this time distinguish between the two kinds of oat smut. 

 This distinction was made by Kellerman and Swingle (1890). They 

 recognized the covered-smut pathogene to be distinct from that of the 

 loose smut, and gave to it the name TJstilago avenae, var. levis, which 

 was later raised to specific rank by Magnus. 



For a brief but rather comprehensive sketch of this early history, one 

 may consult Fischer von Waldheim (1869-70), Kellerman and Swingle 

 (1890), and McAlpine (1910). 



With the exception of the work of Lang (1913), which is discussed 

 later, nothing of very great significance was added to the general fund 

 of information and ideas from 1890 to 1922. During that period the re- 

 sults and conclusions of previous investigators were generally accepted. 

 probably due to the fact that attention was being drawn more toward 

 those diseases for which a satisfactory control had not been discovered. 



PRE-ZADIAN CONCEPTIONS 



Since the work of Zade has thrown new light upon the subject, which, 

 in the writer's opinion, may be considered a turning point in the knowl- 

 edge of the life history of TJstilago avenae, it may be well to coin the 

 phrase pre-Zaelian conceptions and under this as a heading recapitulate 

 the status of the ideas on the subject up to 1.922. Elaboration of details 

 is limited here, only those essentials being presented which will serve to 

 bring to memory the generally accepted conception of the life histories 

 of these smut fungi. It will be evident that there are several conflicting 

 ideas and that much of the earlier experimental procedure in obtaining 

 data has not been in keeping with the course of events as they occur in 

 nature, and. above all, that many of the conclusions are based on mere 

 assumption. 



LIFE HISTORY OP USTILAGO AVENAE 



Inoculation 



The source of inoculum is generally admitted to be the smutted plant 

 in the field at flowering time. The dark sooty masses of chlamydospores 

 in the diseased heads are disseminated by the wind and come in contad 

 with the flowers of the healthy plant. It was held by Jensen (1888: 

 400-401) that only -those spores lodging within the glumes of the 

 healthy blossoms, which are open l'or the purpose of pollination, can 

 play a significant role in infection. This was later confirmed by the work 

 of Clinton (1900:308-309;. and is borne out also by the fact that 



