No. 33.] 369 
spores on a healthy leaf, saw them germinate and bore their way into 
the leaf, and in two weeks the characteristic brown spots appeared, 
with the black specks in due course of time. He found upon the 
fallen leaves in winter what he took to be the same fungus produc- 
ing another set of spores (ascospores), which became ripe in April 
and May. Such fungi are able to keep up a slow growth all winter, 
when higher vegetation is at a standstill. These winter spores prob- 
ably propagate the disease on the new leaves of spring. He also 
found that the fungus is in some instances able to winter over on the 
bud scales* without entering a second stage. The disease affects 
young trees most, and especially those of weakly growth. No rem- 
edy is yet suggested. The same fungus apparently is very common 
on wild and cultivated thorns. 
Lear YELLOWING. 
This disease was observed in a large pear orchard not far from the 
station. By midsummer the leaves began to turn yellow and more 
or less flame colored. Microscopic examination of the tissues of the 
branches showed them very full of starch, but gave no indication of 
the cause of the ditliculty. No fungi were present of any sort, ex- 
ternally or internally. The trees were evidently languishing, and at 
last dropped their leaves long before the usualtime. Thetrue nature 
of the malady might have remained undiscovered had it not been for 
an accidental circumstance. A large pear tree within view of the 
office window showed one of its large lower limbs to be afflicted in 
the manner described, while the remainder of the tree kept its 
healthy green color. The microscopic examination of the tissues, 
the change of color in the leaves, and their early fall, tallied aceur- 
ately with the cases already cited. The clue to the matter was found 
when it was discovered that the limb had been girdled some time 
previously, apparently not within a year, and that this was the line 
of separation between the healthy and diseased parts. The solution 
of the difficulty was plain; the leaf yellowing was due to defective 
nutrition. The orchard where the first named instances were ob- 
served had once been one of the largest in the country, but having 
been seriously depleted by blight, had been put into grass and much 
neglected. Fertilizers and cultivation would doubtless restore the 
trees to normal health. Professor Penhallow* recommends phos- 
phates for invigorating pears, and sulphate of potash as a special fer- 
tilizer. It is plain that individual cases arising from injuries will 
require special treatment. 
DisEasEs of THE APPLE. 
Apple Blight. | | 
It has been shown under the head of pear blight that these two 
a ne eee eee ee ee eS ee 
* Before the Mass. Board of Agriculture, Dec. 1884. See New England Farmer 
for Dec. 13. 
[Assem. Doc. No. 33.] 47 
