1916] FomeEs OFFICINALIS (Vill.) 197 
ordinarily spherical to fusiform and measure from 8-16 X6-10u. The 
intercalary spores may be spherical or elliptical, but sometimes follow 
the shape of the cell from which they are formed and may be almost 
rectangular and up to 22y in length by 6y in width. The rounded spores 
measure up to 104 in width. Figures 15 and 16 show clearly how dis- 
tinctly different the cultures of P. sulphureus are from those of F. 
officinalis, so different that there can be no grounds for the classification 
proposed by Quélet. 
The results of these cultures of Fomes officinalis add another polypore 
to the small list of those in which secondary reproduction is known to 
occur. Brefeld reported a sterile mycelium for 45 species cultured by 
him; 8 were found to produce oidia, two chlamydospores and one conidia. 
Tubeuf®, Fayod®, de Seynes”, Ludwig", Patouillard have found chlamy- 
dospores in about four additional forms, including P. sulphureus, in 
which they have frequently been noted, and Lyman® has recently 
found them in cultures of one other. To these must be added a group, 
probably polypores, the genus Ceriomyces in which chlamydospores 
alone have been observed. 
MYCELIUM. 
This fungus is marked by a peculiarity—shared by few other wood- 
destroying fungi—of forming sheets or masses of mycelium in checks 
or cavities in the wood in which it is growing. Most of the various 
species of xylophilous fungi, as is well known, produce some character- 
istic change in the wood decayed by them. This may consist of distinc- 
tive changes in colour, or consistency, or texture, or localization of 
decay, or extent of decay, or in a tunnelling, or fracturing, etc. The 
mycelium of the majority of species is not evident, except microscopic- 
ally, as it exists only in contact with the cells of the host, and in some 
species disappears altogether in the older parts attacked. Some species, 
however, do form sheets of mycelium, often of considerable extent and 
permanence, in cavities, frost checks, or other cracks that happen to be 
present; thus I have found sheets of the mycelium of Fomes fomentarius 
extending several feet in radial cracks of affected trees. Polyporus 
sulphureus and Fomes officinalis, however, are peculiar in that the wood 
affected by them fractures into more or less rectangular blocks, and 
that the cracks so formed are then filled in with a solid growth of my- 
celium. Cavities formed by other agencies are occupied in the same 
way, so that one sometimes finds masses of considerable volume in wood 
decayed by either of these species. In the case of Fomes officinalis I 
have good reason to believe that cavities may be formed through the 
