154 FUNGI. 
the narrow opening that remains in place of the papilla. In 
normal cases the protoplasm remains united in a single mass that 
shows a clear but very delicate outline. When it has reached 
the front of the opening in the conidium, which is thus emptied, 
the mass remains immovable. In P. densa it is at first of a very 
irregular form, but assumes by degrees a regular globose shape. 
This is deprived of a distinct membrane, the vacuoles that disap- 
peared in the expulsion again become visible, but soon disappear 
for a second time. The globule becomes surrounded with a 
membrane of cellulose, and soon puts out from the point oppo- 
site to the opening of the conidium a thick tube which grows in 
the same manner as the germ-tube of the conidia in other 
species. Sometimes the expulsion of the protoplasm is not com- 
pletely accomplished ; a portion of it remaining in the membrane 
of the conidium detaches itself from the expelled portion, and 
while this is undergoing changes takes the form of a vesicle, 
which is destroyed with the membrane. It is very rare that the 
protoplasm is not evacuated, and that the conidia give out ter- 
minal or lateral tubes in the manner that is normal to other 
species without papille. The germination just described does 
not take place unless the conidia are entirely surrounded by water ; 
it is not sufficient that they repose upon its surface. Besides, 
there is another condition which, without being indispensable, 
has a sensible influence on the germination of P. macrocarpa, and 
that is the exclusion of light. To ascertain if the light or the 
darkness had any influence, two equal sowings were placed side 
by side, the one under a clear glass bell, the other under a 
blacke ed glass bell. Repeated many times, these experiments 
always gave the same result—germination in from four to six 
hours in the conidia under the blackened glass; no change in 
those under the clear glass up to the evening. In the morning 
germination was completed. 
The conidia pf PB. umbelliferarum and P. infestans* show 
an analogous structure. These bodies, if their development be 
normal, become zoosporangia. When they are sown upon water, 
cae sees at the end of some hours the protoplasm divided by 
* This is the mould which prodyces the potato murraip. 
