358 DR, W. R. M‘NAB. 
ruptures, and the innumerable minute spores are set free. 
The spores have when in mass a _pale-yellow colour, and 
a very regular form closely resembling that of the spores of 
Eurotium. In form they are elongated, rapidly narrowed 
towardsboth ends(Plate XVIII, fig. 11). On cross-section they 
appear round, with lateral projections which give them a 
star-shaped appearance. They possess a double wall, the 
outer, a thick ornamented exosporium consisting of two 
valves separated by a deep groove running from pole to pole 
of the spore. Each valve has three or four ribs on the dorsal 
surface, which project but slightly. ‘The spores are 0°0050 
to 0:0060 mm. long, and 0:0040 to 0:0045 mm. broad. 
When the sclerotia begin to ripen they change their colour, 
losing their brown tint, becoming paler, then yellow lke the 
spores. The time elapsing between the formation of the 
sclerotia and their ripening is about from six to eight months. 
The smallest sclerotia germinate as well as the large ones, as 
also do the cohering ones; in the latter case, however, only 
a single cavity containing spores is formed. The sclerotia 
can be dried for some time without losing their vitality, but 
if dried for more than three or four months they were 
killed. 
It remains now only to show that the ascospores again 
produce Penicillium. ‘The ascospores were sown in a carefully 
filtered decoction of dried plums, or in a decoction of red 
currants or gooseberries. ‘The germination occurred in from 
eighteen to twenty-four hours, and was very characteristic 
(Plate XVIII, fig. 12), resembling the germination of the‘spores 
of Eurotium. At first the exosporium ruptures by the swelling 
of the contents of the spores, but it is not thrown off, the 
endosporium protruding like a sac to one part of which the 
exosporium remains firmly attached. The presence of the 
exosporium at once characterizes the germinating ascospore, 
and renders it impossible to confound the germinating asco- 
spores with germinating conidia. From the swollen endo- 
sporium one or two germinating filaments are formed, and 
from these the mycelium springs. ‘The mycelium which 
is produced from the ascospores agrees in mode of growth, 
branching, division by septa—indeed, in every detail—with 
that developed from the conidia, so that the description of 
the one applies equally to that of the other. Next day 
the mycelia develop conidia as in ordinary Penicillium- 
mycelia. 
The ascospores retain their vitality for a very long time. 
After being kept dry for two years a few ascospores germi- 
nated, but most of the spores had fallen into two halves. 
