344 Report of the Horticultural Department op tub 



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 dei>osited, as a result of the partial girdling of the limib. 



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. Ohas. 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. iSeveral experi- 

 menters have 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. 



The leaves of ap^ple trees are occasionally attacked by a Sphce- 

 rojjsis^ when injuries appear in the form of round brown dead 

 spots somewhat like those from burning hj improper spraying 

 with Paris green. This form of Sphceropsis has not been 

 definitely proven to be identical with 8. 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 Sphceropses that occur on various plants. Cultures 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 develoi>ed 

 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.) 



»Aun. Kept. N. Y. State Mus. Nat. Hist., 1881, p. 36. 



