- Species of 
os cked by the knot. “ Prunus serotina Ehr., the rum-cherry, 
At i oe le i yi RTS Ba raat pe ree! he eg Oe RG nee eee a k ee ee i, 
ar nad Mee ga pes TATED, eel See SaaS ne Pe ee er 
a a = ile RESTET r AEE 
Ae i a a Sr a E EEEE oa E A uart eer i z r ote ae! a : i : ; 
1876.) The Black Knot. 345 
Schweinitz was the first to describe, under the name of Spheria 
morbosa, the fungus causing the black knot. At that time noth- 
ing was known of the secondary forms of fruit of this group of 
fungi. Mr. ©: H. Peck was the first to describe the conidia. 
From a short discussion as to the position this species should 
take in classification and the name it ought to bear, it is con- 
cluded that until its related species are better known its old place 
and name had best be retained. 
The black knot is far from being of recent origin, and has 
furnished a subject about which vastly more has been written 
than was known. Many, especially the early writers, held it to 
be of insect origin, while, later, others have looked upon it as a 
vegetable growth, and still others included in its production the 
actions of both these forms of life. During the last thirty years 
the insect theory has been gradually given up by the entomolo- 
gists; but it still remains for many fruit-growers to accept the 
knot as being of fungus origin. The proof given in the paper is 
very conclusive on this long-disputed point. ‘ First, the knots 
do not resemble the galls made by any known insect. Secondly, 
although insects, or remains of insects, are generally found in old 
knots, in most cases no insects at all are found in them when 
young. Thirdly, the insects that have been found by entomol- 
ogists in the knots are not all of one species, but of several dif- 
ferent Species, which are also found on trees which are never 
affected by the knot. On the other hand, we never have the 
black knot without the. Spheria morbosa, as was admitted by 
Harris; and the mycelium of that fungus is found in the slightly 
Swollen stem long before anything which could be called a knot 
has made its appearance. Furthermore, the Spheria morbosa is 
hot known to occur anywhere except in connection with the 
knots,” 
Those who believe that there are two distinct species of the 
knot have arrived at this conclusion from a too hasty generaliza- 
tion upon incomplete observations. “ Having seen some cherries 
free from the knot, although growing near diseased plum-trees, 
and others, perhaps not near any plum-trees, covered with knots, 
they have jumped at the conclusion that there must be two dif- 
ferent fungi producing the knot: one on the cherry, derived from 
the wild cherry ; another on the plum, derived from the wild 
plum,” This false inference comes from the fact that some 
wild cherry, and also some cultivated varieties, are not 
k 
