Some Bacterial Diseases oe Plants. 5 
in little bead-like droplets and there hardens into small, amber- 
colored scales. Again it appears to dry uniformly over the sur¬ 
face, or just beneath it, and there produces a dark brown, resinous 
surface, which blackens with age. • Such stems are very brittle and 
easily broken, which fact makes it almost impossible to handle the 
crop without an immense amount of shattering. 
The leaves attached to the diseased part of the stem usually 
show the watery, yellow color at the base and especially in their 
tiny petioles. The leaves on those parts of the stem which are 
blackened are always dried up, yellow, and extremely brittle. The 
stipules at the base of the petioles are yellow and brittle, and show 
the disease before their corresponding leaves. 
One year old plants exhibit blackened areas in the crown and 
black streaks running down into the tap root. As the plant grows 
older this blackening increases until the whole crown is involved, 
and either the crown buds are destroyed or the root is no longer 
able to perform its functions, and death follows. 
So far as our present observations go, the disease appears to 
run its course with the first cutting, and those plains which have 
sufficient vitality throw out a good growth for the second and third 
cutting. Strange as it may seem, there is little or no trace of the 
blight during the remainder of the season, but in the following 
spring an aggravated outbreak may be expected. The disease ap¬ 
parently does not kill many plants the first year, but they begin to 
die after the blight has been prevalent more than one season, and 
after two or three years so many of them may be missing that the 
stand is practically worthless. 
At present, we are at a loss to explain satisfactorily why the 
first cutting, only, should be attacked, unless it is that by pasturing 
cattle on the alfalfa field during the winter, the constant tramping 
splits open the crowns and bruises the young, tender shoots so that 
during the first irrigation, soil containing the disease germs is 
washed into this injured tissue. The weather conditions at this 
time of the year are, as a rule, unfavorable to a rapid, vigorous 
growth of the plant, and it is probably in a hyper-susceptible condi¬ 
tion. This explanation is borne out, first, by the fact that the dis¬ 
ease has not been observed to occur until after the first irrigation; 
and second, by the fact that since no cattle are allowed in the field 
after the first cutting, the young crown buds of the second crop 
have received no mechanical injuries through which they might be¬ 
come inoculated. Again, the plants themselves are in a more vigor¬ 
ous, resistant condition at this season of the year. 
Future experiments alone will demonstrate whether it will be 
possible to prevent the disease upon the first cutting by keeping 
stock off the land during the winter and early spring, and by so doing 
