184 A Mushroom Disease. [Sess. 
work of filaments, whereas when diseased the branches are 
much fewer in number. 
When the beds begin to produce mushrooms there is no 
sign of disease, the crop being apparently healthy, and con- 
tinuing so for a period of from two to three weeks, but 
examination of the spawn reveals the presence of the fungus, 
and within a month distorted mushrooms begin to grow. 
The first of the diseased specimens are all of the first type, 
but as time passes a few may be seen_here and there in which 
development of the cap has commenced, and then growth has 
been arrested, the result being a stout, fully-formed stalk 
terminated by a small cap. Later in the history of the bed 
the last stage appears, and the mushrooms show no trace of 
differentiation into stalk and cap, but resemble clumps of 
puff-balls. It must be noted, however, that when a bed 
is completely overrun with disease apparently healthy mush- 
rooms develop here and there. The gradual transition from 
the fully developed but diseased type to the completely 
hypertrophied condition seems to indicate the struggle that is 
going on in the bed between the mushroom: mycelium and 
that of the fungus. It seems as if the vigour of the mush- 
room spawn in the earlier period of the existence of the bed 
allows the mushrooms to outstrip the disease for a week or 
two, but that, owing to the gradual lowering of the tempera- 
ture of the bed, and the slightly diminished food-supply, the 
vigour of the spawn is not so great as at first, and it is more 
susceptible to the attacks of the fungus. The result is that 
perfect mushrooms become fewer, the disease spreads in 
those that are developing, it ultimately obtains the mastery, 
and the mushroom spawn is entirely killed out.’ 
Sections were made from mycelium, stalk and cap of 
diseased specimens, and examined either unstained or stained 
with bismarck brown or Loeffler’s blue. When examined 
under the microscope thick hyphz with dense contents could 
be seen running through the tissue of the mushroom. These 
were usually more numerous in the stalk than in the cap, 
and with the blue or brown stain used they assumed a 
darker hue than the surrounding tissue (fig. 13). The 
1 Spawn from badly diseased beds failed to develop on sterilised stable manure, 
while healthy spawn from test-beds at Bangholm Nursery developed freely. 
