New YorK AGRICULTURAL EXPERIMENT STATION. 233 
a somewhat similar yellowing of the foliage. So far as our observa- 
tions go, the character of the soil has no marked influence. In 
the affected field on the Station farm the soil is clay loam, with 
good surface- and under-drainage. Alfalfa has been grown suc- 
cessfully on this field during the greater part of the past fifteen 
years without any previous trouble of this kind so far as can be 
learned. | 
Yellow top is sometimes mistaken for leaf spot. Although both 
diseases cause the foliage to turn yellow the two should be dis- 
tinguished without difficulty. Plants affected with yellow top show 
green leaves below and yellow leaves above; whereas those affected 
with leaf spot have yellow leaves below and green leaves above. 
Besides, in yellow top the leaves are free from spots and do not 
fall; while in leaf spot the leaves are thickly covered with small 
brown spots and fall prematurely. Of course, the two diseases 
may occur together. 
A disease which may have been yellow top is said by Elliott®® 
to have greatly shortened the yield of alfalfa hay in Washington 
in 1906. 
PITTING OF THE TAP-ROOT. 
The tap-roots of alfalfa plants in this State are quite commonly 
covered with brown pits and scars of various shapes and sizes. 
On the roots of old plants’ the scars are suggestive of the potato 
scab disease and one might easily believe that they are due to the 
attack of some parasitic fungus; but on the roots of plants one and 
_twe years old it is plain to be seen that the bark has been gnawed 
by some insect or animal. (Plate XXVII, fig. 2) Although the 
growth of the plants does not appear to be seriously checked the 
effect of the pitting cannot be otherwise than harmful. In the 
aggregate, the damage done must be considerable, for the trouble 
is exceedingly common. 
BUNDLE BLACKENING IN THE TAP-ROOT. 
Black or brown streaks within the tap-root are of frequent oc- 
currence. The black streaks are discolored fibro-vascular bundles. 
_ The cause of the discoloration is unknown. So far as can be de- 
termined from microscopic examination neither bacteria nor fungt 
are to be found in the blackened bundles. Whether the bundle 
blackening indicates a diseased condition of the tap-root cannot 
be definitely stated. It often occurs in the roots of thrifty, ap- 
parently healthy plants. 
MBlliott’ (27; ps 31): 
