LEAF-SPOT OF ALFALFA AND RED CLOVER. 35 
ited amount of evidence indicates that the fungus is not carried 
with the seed. Yet the fact of the almost universal occurrence of the 
disease in remote localities is well established. The explanation of 
this fact still furnishes a very interesting and apparently very 
difficult problem. 
SUMMARY. 
(1) One of the most important diseases, if not the most important 
foliage disease, of alfalfa is the leaf-spot caused by the fungus 
Pseudopeziza medicaginis (Lib.) Sacc. A similar but less important 
leaf-spot of red clover is caused by the fungus Pseudopeziza trifolii 
(Biv.-Bern.) Fckl. The morphological differences between these 
fungi are so slight that doubt has frequently been expressed whether 
they are not identical. Several conflicting opinions as to the life 
histories of these fungi are found in mycological literature. This 
study attempts to determine the relationship of the two fungi here 
mentioned and to trace as far as possible their life histories in rela- 
tion to their host plants. 
(2) Pseudopeziza medicaginis on alfalfa and Pseudopeziza trifolii 
on red clover have been obtained and studied in pure culture. Efforts 
to cross these fungi from one host to the other have not been success- 
ful. Morphological as well as physiological differences have been 
found which in the opinion of the writer justify retaining the fungi 
as distinct species. 
(3) None of the imperfect fungi which have been regarded as a 
stage in the development of these fungi have been found to be re- 
lated. Apparently no other spore form than the ascospore occurs 
in nature. 
(4) Infection is produced by the direct penetration of the germi- 
nating ascopores through the cuticle and epidermal cell wall of the 
leaf. ■ The mycelium developing into a small stroma about the point 
of entry produces in about two weeks an apothecium. 
(5) The fungus lives over winter on dead leaves which escape 
decay, and ascopores produced in the spring furnish the source of 
new infection. 
(6) Efforts to exclude the disease from alfalfa fields sown in 
localities remote from other alfalfa by the surface sterilization of 
the seed have given no degree of success. Evidently, in these experi- 
ments at least, the fungus was not carried on the surface of the seed — 
probably not with the seed at all. The demonstration of the source 
of infection in such fields still furnishes an interesting problem. 
