2 BULLETIN 759, U. S. DEPARTMENT OF AGRICULTURE. 
method of overwintering- of the fungus has not been conclusively 
demonstrated; and the oft-considered question whether this fungus 
is identical with or merely similar to one which causes a correspond- 
ing leaf -spot on red clover has never been decisively answered. It 
is because, of the last consideration that the two diseases have been 
studied together. The leaf-spot of red clover caused by the fungus 
Pseudopeziza trifolii occurs over a wide range of territory, but 
usually not so abundantly as that on alfalfa. Mention of it occurs 
frequently in literature. Xo distinctive common name has been ap- 
plied to it. Much of the later interest in this disease is in connection 
with the question whether or not red clover is a source of infection, 
producing destructive outbreaks of leaf-spot on neighboring alfalfa 
when this plant has been introduced into new localities. 
Leaf-spots of a nature very similar to the two already mentioned 
and commonly reported to be caused by the same fungi are known 
on a long list of clovers, alfalfas, and closely related plants. All of 
these diseases should be studied together and the relationship of the 
causal organisms determined. However, most of them do not occur 
in America or only in restricted localities, and none of them causes 
great damage to the host plants. The only one of these of which any 
living material has been available for study is that caused by 
Pseudopeziza medicaginis on Medicago lupulina. The incomplete 
notes on this disease have been included. 
THE DISEASES. 
ECONOMIC IMPORTANCE. 
As has already been stated, the assertion has been made again and 
again that leaf-spot is the most common and destructive of the 
foliage diseases of alfalfa. That it is the most common is beyond 
question. But in the estimates of the loss which it has caused it 
appears highly probable that damage from other causes than the 
conspicuous leaf -spot has been included. Nevertheless, even if proper 
deductions for these inclusions could be made it might still be true 
that leaf -spot causes greater loss than any other foliage disease. 
The highest estimate of loss from this disease is that of Pammel 
(1891) x from Iowa. In 1S90 he attributes to this cause a loss of 
half the crop. Stewart and others (1908. pp. 38±-3S7) report from 
Xew York that young stands are often ruined and that old stands 
are killed outright. Chester (1891) reports that some plats at the 
Delaware station in 1889 were attacked severely before the plants 
were large, and some of them were completely destroyed. Yoges 
(1909) in Germany and Ivy Massee (1911) in England note the 
sickly appearance of diseased fields. 
1 The dates in parentheses refer to " Literature cited " at the end of this bulletin. 
