BULLETIN OF THE BUSSEY INSTITUTION. 107 
We have not yet been able to procure any specimens of the Californian 
disease. 
Besides the specimens in which the knots were actually or presuma- 
bly caused by Spheria morbosa, a large number of knots have been 
received whose origin is very obscure, and although our entomological 
friends to whom specimens were submitted were not confident that 
they originated in consequence of the sting of any insect, yet they 
certainly do not seem to have been caused by a fungus. <A peculiar 
excrescence, bearing a very close resemblance to the true Black Knot, 
was sent by Professor Thomas Meehan, in the spring of 1876, who 
wrote that it was common on the flowering almond, Amygdalus nana, 
var., near Philadelphia. The knot is black and rough on the outside, 
and the resemblance to branches of the plum when attacked by Sphe- 
ria morbosa is very striking. The interior of the knot is hard and 
solid, and microscopic examination does not show the presence of any 
fungus. On the surface, several fungi were found, but they were the 
sterile conditions of certain common Spheriacee such as are usually 
found on exposed bark. As far as can be ascertained, the flowering 
almonds in the region of Boston are free from knots like that just 
_ described. 
A common excrescence which is associated in the popular mind with 
the Black Knot of plum-trees is found on species of Carya, especially 
Carya tomentosa, near Boston. Some trees are covered with knots vary- 
ing in size from that of a filbert to as large as a good-sized orange. 
They are sometimes so numerous as in winter to render the trees on 
which they are growing very conspicuous. They are generally attached 
laterally to the branches, but occasionally encircle them, and are lobed 
and rough on the surface, but not often of a black color. Microscopic 
examination fails to show any traces of a fungus in the very hard sub- 
stance of the interior. A section of the younger knots usually shows 
traces of a bud-like structure, and the knots, which in young specimens 
seem to have occupied the position of a bud, look as though they were a 
shortened and monstrously developed axis. It would be very desira- 
ble to examine very young stages of the excrescences, but, although 
we have found knots of quite small size, they always seemed to be at 
least several months old, and we have not yet been able to recognize 
the disease in its earliest stages. The larger knots seem to be several 
years old, and apparently the disease, whatever its origin may be, 
