344 Report oF THE HORTICULTURAL DEPARTMENT OF THB. 
is large the normal activity of the branch is seriously interrupted. 
The swelling of the bark is probably caused by an excess of food 
being deposited, as a result of the partial girdling of the limb. 
When the twigs are attacked a portion of the new growth may — 
be killed in much the same manner as when attacked by pear 
blight. Much damage may result from such attacks and the 
fungus may occur in orchards where there is no evidence of 
cankers on the larger limbs. | 
Black rot of apples was first brought to the attention of the 
public by Dr. Chas. H. Peck! in 1881. Since then the disease 
has been found also on pear and quince fruit; and at the present 
time black rot is a common orchard disease. Several experi- 
menters nave proven the identity of the fungus as it occurs on 
the three hosts. Our experiments prove that the black rot fungus 
and the canker fungus are identical. 7 
The leaves of apple trees are occasionally attacked by a Sphe- 
ropsis, when injuries appear in the form of round browm dead 
spots somewhat like those from burning by improper spraying 
with Paris green. This form of Spheropsis hag not been 
definitely proven to be identical with S. malorum, but the 
indications are that it is the same. 
EXPERIMENTS IN 1900. 
The inoculation experiments with cultures of the canker 
fungus were continued for the purpose of confirming former 
results and to determine, if possible, the relationship between 
the Spheropses that occur on various plants. Oultures were 
made from cankered apple-tree limbs and from decaying apples. 
Trees of various kinds were inoculated with these cultures, as 
given in the table below. A flamed scalpel was used in making 
incisions in the bark, then some of the fungus as it had developed 
in the cultures was inserted in the wounds. Check wounds 
were made in the same manner but not inoculated, and all 
wounds were protected with grafting wax. (See Plate LIV.) 

*Ann. Rept. N. Y. State Mus. Nat. Hist., 1881, p. 36. 
