444 BULLETIN OF THE BUSSEY INSTITUTION. 
head of spermagonia. Plate VI., Fig. 2, represents a section through 
a cavity hardly distinguishable externally from the perithecia, which, 
instead of being filled with asci, is lined with slender filaments, whose 
tips are somewhat incurved, and easily break off, the central part of 
the sac being filled with them. We call these spermagonia, from their 
resemblance to the bodies of the same name in lichens. They are much 
less common than the conidia, or stylospores. Interspersed amongst 
the ascus-bearing perithecia, one finds, tolerably frequently, still other 
cavities which are much more flattened than the perithecia; which 
often, instead of appearing oval, on section, seem almost triangular. 
They are lined with short, delicate filaments, which end in a minute 
oval, hyaline body. These small oval bodies are produced in immense - 
numbers, and are discharged not singly, but in masses. ‘They are 
more or less closely held together by a sort of jelly, and ooze out 
from the cavity in which they were produced in the form of tendrils ; 
reminding one of the toy called “ Pharaoh’s serpent.” We have watched 
the emptying of these bodies, to which we must apply the somewhat 
vague name of pycnidia, and have found that it sometimes takes as 
long as two minutes for them to discharge their contents. 
If we turn now from the knot on the choke cherry to that on the 
cultivated cherry and plum, we find a slight difference of aspect, so 
that, without much trouble, one can say whether a certain knot comes 
from a cherry or a plum tree. The difference is, however, slight, and 
not greater than would arise from the different character of the bark 
through which the fungus has to make its way. A microscopic 
examination of the knot, in its different stages, shows absolutely no ~ 
difference between the fungus on cherries and on plums. ‘The conidia 
are the same, and appear at about the same time; the ascospores are 
identically the same in both cases, and ripen at the same time; and — 
the mycelium is the same. In short, the microscope fails to show any 
difference ; and, if to the naked eye there appears to be any, it is, 
as we have said, owing either to the different histological character 
of the stems of the two trees, or to the greater luxuriance of the 
growth on one tree than on the other. On the whole, the fungus 
does not thrive so well on the plum as on the choke cherry, as is 
shown by the fact that fewer perithecia are formed on the former 
than on the latter, —a fact observed long ago by Schweinitz. 
