1G 



James G. Horsfall 



Figure 2. spots on leaves of red clover caused by macrosporium sarcinaeforme 



acteristic concentric zones of full-sized spots, as shown in figure 2, make 

 the disease almost unmistakable in the field. In young stages the spots 

 are extremely difficult to distinguish from those caused by Pseudopeziza, 

 but a careful examination usually will reveal a hint of the zonation. The 

 older Pseudopeziza spots bear in their center the diagnostic sign of that 

 disease, the minute dried apothecium. The latter spots are frequently 

 dendritic in outline, but such a characteristic never occurs with the Macro- 

 sporium leaf spot. 



Etiology 



Name, history, and classification of the pathogene. The pathogene was 

 first described by Cavara (1890) at Pa via, Italy, as Macrosporium sar- 

 cinaeforme. Twenty-five conidia from one specimen collected at Ithaca 

 measured 23.4 to 32.4 M (mean 28.01 ± 0.026) by 19.8 to 25.2 M (mean 

 23.39). The original measurements of Cavara are 24 to 28 /j, by 12 to 18 /jl. 

 Krakover (1917:328) measured many spores from several different pure 



