BULLETIN OF THE BUSSEY INSTITUTION. 449 
assert that the knot was caused by a fungus rather than an insect, 
although his belief that the fungus originated in a morbid condition of 
the plum itself was incorrect. In the second edition of his “ Insects 
Injurious to Vegetation,” Harris is somewhat non-committal, although 
he goes so far as to admit, that, “ whatever be their [the knots | origin and 
seat, they form an appropriate bed for the growth of numerous little 
parasitical plants or fungi, to which botanists give the name of Spheeria 
morbosa.” He also significantly adds: “It is worthy of remark, that 
they are sure to appear on the warts in due time, and that they are 
never found on any other part of the tree.” 
More recently, the belief in the insect origin of the knots has been 
given up by entomologists, although it is still generally held by 
fruit-raisers. One of the most prominent entomologists who has, in 
recent years, written on the nature of the black knot, is Mr. B. D. 
Walsh.* He is of the opinion that the knot is not caused by any 
insect, but by a fungus whose spores ripen in July. From this state- 
ment, we might infer that he had jeen the conidia, although he does 
not describe them so that they can be recognized. If, however, what 
he saw were the conidia, his statement that they extend down over 
the stem below the knot is incorrect. He went too far in asserting 
that there were two distinct kinds of black knot: one on plums, and 
another on cherries. He was led to this conclusion, apparently, rather 
by statements of other persons as to the communicability of the dis- 
ease from plums to cherries, and vice versé, than from any direct 
observation on the structure of the knot. In a review of Walsh’s 
article,t the writer goes still farther from the fact in suggesting that 
there is a third kind of fungus on .Prunus Chickasa. 
The best and so far as we know the only correct statement of the 
etiology of the black knot, was made by Mr. C. H. Peck,t who, as we 
have already remarked, was the first to describe the conidial state of 
the fungus. He also first showed definitely when the ascospores 
ripened, and correctly reasoned that the knot was caused by the 
Spheria morbosa, and that the fungus on plums and cherries was the 
same. 
* The Practical Entomologist,” March 26, 1866, and March, 1867. 
t “Entomologist and Botanist,” Vol. IL, p. 231. 
t A Paper on Botany read as a Report before the Albany Institute, 
February 6, 1872. 
VOL. I. 57 
