346 The Black Ka [June, 
and Prunus Virginiana L., the choke-cherry, are about equally 
common near Boston. The latter is very frequently attacked by 
the knot; the former never, as far as our experience goes, and 
we have examined hundreds of trees.” In and around Boston 
the cultivated plum has been nearly destroyed by the knot, while 
over the same territory the wild plum is of rare occurrence, if 
found at all, showing that the disease must come from some 
` species of cherry. 
In all this long discussion of the black knot much confusion 
has grown out of the loose use of popular names. The choke- 
cherry of one person may not be the choke-cherry of another; 
and the bird or rum cherry in one section may bear other names 
in another part of the country. : 
With a knowledge of the nature of this contagious disease 
the remedy at once suggests itself: namely, to cut off the knots, 
together with the swollen portions of the branches, wherever and 
whenever they are found. In autumn, as soon as the leaves fall, 
the knots can be most easily seen, and all branches bearing them 
should be taken off and burned at once. Though the ascospores 
are not formed until late in the following winter, it was carefully 
observed that, were the knots left undestroyed, they would ripen 
after the branch was cut from the tree. The choke-cherry, bird- 
cherry, and wild plum furnish means for rapid propagation of the 
knot, and they should be gladly sacrificed for the good of their 
more worthy allies. Of the choke-cherry the writer says, 
“ However opinions may differ as to its beauty, there can be only 
one as to its injurious influence on cherry and plum orchards ; 
and it cannot be too strongly impressed upon fruit-growers that 
the choke-cherry is a most dangerous enemy, and should be de- 
_ stroyed.” 
Knowing the cause, nature, and means of propagation of the 
black knot, it remains for the fruit-growers to profit by their 
valuable instruction and use their best endeavors to destroy this 
st. The article closes with a statement of the importance 0 
keeping the disease within its present bounds. It is now peculiar 
to America, and any means of introducing it into other countries 
should be strenuously avoided. 
EXPLANATION OF THE PLATES. 
. mn 
Plate III. Figure 1. Sphæria morbosa on the cultivated plum, as seen in autumn, — 
natural size. i ‘x hundred 
Figure 2. Section of knot on the choke-cherry in May, magnified six 
diameters ; a, mycelium ; b, conidia. , 
