A Study of Meadow-Crop Diseases in New York 65 



was described on alfalfa by Pollacci from Italy three years later (1902:51). 

 The Italian fungus was first reported in America by Melchers (1915:536), 

 and Jones (1916) a year later confirmed the determination by comparing 

 it with original material. Von Hohnel (1918:162-163) erected a new 

 genus, Pseudoplea, on Pleosphaerulina briosiana because he believed the 

 perithecium to be formed in a unilocular stroma and to have no true 

 ostiole. He describes the ascospores as hyaline and muriform. 



Three years later Petrak (1921:28-29) removed Pseudoplea from the 

 Pseudosphaeriales where von Hohnel had placed it and transferred it to 

 the Sphaeriales because he maintained that the perithecium had a true wall 

 and a true ostiole. He went one step further and reduced all these names 

 as follows: Sphaerulina trifolii Rostrup (1899), Pleosphaerulina briosiana 

 Pollacci (1902), Pleosphaerulina briosiana Poll. var. brasiliensis Puttem. 

 (1905), and Pseudoplea briosiana (Poll) v.H. (1918) to synonyms of 

 Pseudoplea trifolii (Rostr.) Petrak. 



Petrak very probably is correct in combining the organisms on clover 

 and alfalfa under the same species. The only point of separation has been 

 the hyaline spores in clover and the yellow ones in alfalfa and " the 

 universal absence of a longitudinal cross wall in the spores of the clover 

 organism, and the almost invariable presence of the same in the spores of 

 the alfalfa organism" (Miles, 1925:686). Miller (1925:226), however, 

 shows that the spores of the alfalfa fungus become muriform late in their 

 development only and are hyaline when normally discharged, becoming 

 colored only when the light strikes them. The writer, furthermore, has 

 found muriform spores in single spore cultures of the organism isolated 

 from white clover. It appears therefore that spore color and septation are 

 dependent upon the environment rather than upon any innate properties 

 of the organism itself. 



Miles (1925) distinguishes the form on Medicago maculata as Pseudoplea 

 medicaginis, on insufficient grounds as it appears to the writer. The three 

 characters that he stresses in separating it from Pseudoplea briosiana and 

 Sphaerulina trifolii are: differences in spore size (page 688); the presence 

 of a more evident and a wider sterile border of the thalli on agar cultures, 

 as well as greater abundance of sclerotial bodies (page 681); and on results 

 of inoculation experiments (page 683). The differences between his spore 

 measurements are so small that a mathematical computation of his figures 

 probably would not show them to be significant. The averages, for 

 example, are: alfalfa organism, 31 by 12/*; clover organism, 34 by 13/x; 

 and the bur-clover organism, 35 by 13.5/x. With regard to his inoculation 

 results, it is sufficient to state that the bur-clover organism infected alfalfa 

 and the three species of Trifolium successfully. Conversely, spores of the 

 white-clover organism produced infections on alfalfa and bur clover. The 

 differences in severity of infection which he reports for the three forms on 



