166 
POPULAR SCIENCE REVIEW. 
Apropos of the suggestion which has been offered through 
the medium of a horticultural newspaper, that the “black rot” 
appears to be the mycelium of some fungus, it will be sufficient 
to remark that the term “mycelium” is, by general consent, 
confined to productions which consist of barren threads. The 
presence of spores, in this instance, clearly removes the pro- 
duction beyond the limits of the term “ mycelium.” Unless 
terms are employed with their recognized meaning and limita- 
tions, some explanation should accompany their use to prevent 
misconception. 
The conclusion at which we have arrived appears to us the 
most tenable one, that the fuugus in question belongs to the 
Hyphomycetes , or moulds. In habit and external appearance 
it strongly reminds one of the white mould which precedes 
many species of Erysvphe , such as the one so common on peas 
in the autumn, or that which precedes Uncinula on the leaves 
of the maple. Even under the microscope there seems to be 
some kind of relationship ; the interwoven, septate, colourless 
branched threads are present, but there is an addition of a 
somewhat gelatinous medium, which binds the threads together 
into a pellicle. The spores and their mode of production are 
different, and this, in the Hyphomycetes , is a most important 
distinction. In Oidium the spores are produced in chains, in the 
present species singly. It is very true that the structure, as seen 
in a drawing, resembles closely that of some species of Zygo - 
desmus , but there is a peculiarity in the threads of many of the 
species in that genus that the threads are cut, as it were, nearly 
through at short distances, or abruptly bent, of which there is 
not the slightest indication here. The spores are very similar 
in size and form, but there are two or three features which 
appear to us conclusive for rejecting the coffee rot from 
this genus. In all the species of Zygodesmus the threads are 
free from any investing medium, the spores are pulverulent, 
and, moreover, the threads are more or less coloured. Further 
than this, all the species occur on dead wood or leaves, and in 
no instance is a species parasitic on living leaves. Although 
too much reliance is not to be placed on this fact, it is never- 
theless noteworthy that in genera in which the species are para- 
sitic on living plants there is seldom an exception to this rule, 
and so in genera which contain species found on dead sub- 
stances parasitic species are not found. In illustration of the 
former we may cite Peronospora , Ramularia , and Evysiphe , 
and of the latter Dactylium , Sporotrichum , and Zygodesmus. 
The presence of the gelatinous element which binds together 
the threads and spores into a thin pellicle, which is easily 
separable from the matrix when moist, is an important feature 
in determining the affinities of the “ coffee rot.” In the genus 
