No. 104.] 121 



ferred to the genus Plowrlghtia, and this later generic name will 

 probably ere long be generally accepted. 



The specimen sent is of a brown color, for it is not until late in 

 July or about the 1st of August that it presents its well-known 

 black appearance, caused by "numerous coal-black hemispherical 

 plates of about the size of the head of a pin, each of which is a dis- 

 tinct fungus.'' 



Professor Riley has quoted Mr. "Walsh as having shown that the 

 black-knot fungus infesting the cultivated cherry " was quite dis- 

 tinct from that attacking the cultivated plums." He has also indi- 

 cated another species occurring uj3on the "Miner plum," which, 

 may be seen " at a single glance to be essentially distinct from the 

 common black-knot of the plum." He writes : " It would seem to 

 follow that there are three distinct black-knots, originating, respect- 

 ively, from choke-cherry, from the common wild plum and from 

 the Chickasaw plum " [American Entomologist, ii, p. 231). 



Those who have studied this fungus the most thoroughly believe 

 in the existence of but one species, which readily tranfers itself from 

 the plum to the cherry, and the reverse. According to Professor 

 Peck, State Botanist, " it is now known to occur on Prunus domes- 

 tica, P. Americana^ P. cerasus, P. Yirginiana, P. Pennsylvanica, 

 and P. serotina. Two of these are plum-trees — ^ one introduced, 

 the other native — and the remaining four are cherry-trees, of 

 which the last three are indigenous" (31st Report of the N. Y. 

 State JIuseum of Natural History^ 1879, p. 60). 



Remedy. — The only remedy, so far as known, of the black -knot 

 is the free use of tlie knife as early as possible after its discovery. 

 Mr. Walsh has emphasized the following as the remedy that may be 

 relied on : " If the diseased twigs are cut o£E and destroyed early 

 in July in the latitude of New York, or a little earlier or later 

 according to the latitude, taking care to cut a few inches below the 

 affected part, the black-knot can be checked and probably entirely 

 eradicated ; but if this operation is delayed until August, it will be 

 of no benetit whatever." 



If the above remedy is resorted to in the early stage of growth, 

 the limb or twig need not be removed, but the fungus can be cut 

 out with a sharp knife while still confined to one side of the branch, 

 permitting, if properly done, the wound to heal in a short time. 



[Assem. Doc. No. 104.] 16 



