1900-1901. | A Mushroom Disease. 185 
hyphe in sections taken from the thicker parts of the 
mycelium were invariably thicker than were the hyphe in 
the stalk or cap of the mushroom (see fig. 14). On making 
sections at the outside of the mushroom the hyphe could be 
seen growing out. When they reach the surface they assume 
a different form. The filaments (fig. 15a) are almost erect, 
more delicate than the hyphe in the tissue of the mushroom, 
and produce from two to seven whorls of branches, all of 
which taper off gradually to a point, each bearing at the 
end a bud (conidiospore) (fig. 150). The conidia are uni- 
cellular, and vary in size, the smallest being 4x 1°50, while 
the largest are 7 x 2°75. 
I have previously stated that the beds produced apparently 
sound mushrooms. These, on examination, were found to 
contain a few hyphe of the fungus, and I therefore conclude 
that such mushrooms were formed from an exceptionally 
vigorous portion of mycelium, and although attacked by the 
disease they had outstripped it. 
The fungus is evidently a Verticilliwm allied to V. agari- 
cinum, Corda. . V. agaricinum has whorls of branches similar 
to the plant under notice, but these branches produce secondary 
whorls, a condition I have not observed in the species from the 
tunnel. Verticillium’ is a form of the genus Hypomyces, and 
as I am at present growing the Verticillium under various 
conditions in the hope of obtaining the Hypomyces stage, I 
refrain from expressing an opinion as to the exact species. A 
disease due to a similar parasite has appeared on mushroom 
beds in England? Austria,> Frances and Germany.’ Cooke 
found a Mycogone along with the Verticilliwm, the former 
being the chlamydospore and the latter the conidial stage. To 
this he gave the name (under reservation) of JZ alba. Stapf 
found the Verticilliwm alone in the Vienna specimens. This 
1 De Bary, Comparative Morphology of the Fungi, Mycetozoa and Bacteria, 
(trans. H. E. F. Garnsey), p. 245. 
2 Cooke in Gard. Chron., 3rd series, vol. v., 1889, p. 434. 
® Stapf in K. K. Zool.-Bot. Gesells. in Wien., Bd. xxxix., 1889 ; Abh., p. 617. 
4 Costantin et Dufour, Rev. gen. de botanique, tome iv., 1892, pp. 401, 462, 
549; Comptes Rendus de Il’Acad. des sci., tome exiv., 1892, p. 498; Bull. de la 
soc. bot. de France, tome xxxix., 1892, p. 143; Prillieux, Bull. de la soc. bot. de 
France, tome xxxix., 1892, p. 146. 
5 Magnus, Bot. Centralblatt, Bd. xxxiv., 1888, p. 394. 
