55 
are always one-celled and colorless (Fig. 2). The smooth, delicate spore 
membrane is surrounded by a gelatinous envelope. The spores measure 
0-14 by 5-6/*, agreeing with the measurements made by Fuckel and Sac- 
cardo. They germinate in a few hours in water or a nutrient solution, 
and develop a germ tube which soon branches and forms septa; the 
cells lying next to the spore swell more or less. 
A mycelium is formed in a few days by means of the rapid growth of 
the germ tube and repeated branching. The hypliae are of unequal 
diameter, and are made up of short, often somewhat swollen cells. 
When the mycelium grows in a nutrient solution gonidia are formed 
after some time. The short cells of the thicker hyph® develop out¬ 
growths which are cut off, the mother cell and gonidia both being filled 
with dense protoplasm; or on the other hand, the hyphse cells may first 
develop basidia, which cut off spores from the end. Both forms of de¬ 
velopment may occur simultaneously on the same liyplne. The gonidia 
themselves are alike, and agree in form and size with those produced 
on the leaf excepting that they are a little more regular. From this, 
and from the fact that the gonidia are produced more abundantly where 
the hyphse are more closely interwoven, we may conclude that the goni¬ 
dia produced in culture on the slide are homologous with those pro¬ 
duced on the leaf, and that the hymenium not attaining to the same 
degree of development is due to the changed mode of growth. This 
question can not be definitely decided, for tbe fungus on the*slide did 
not develop farther, and attempts at infection were without result. 
Leaves of Platanus were infected with the Glceosporium in the most 
varied ways—upon the upper and lower surface, upon young and old 
leaves, on detached branches and uninjured trees; the cultures were 
kept moist and dryland the germinating power of the spores was con¬ 
trolled by cultures on slides, but not a single infection gave a positive 
result. It can therefore at present only be said in regard to the life 
history of the Gloeosporium nervisequum that the gonidia will produce 
a similar gonidial stage on the slide. 
Is it possible, then, to draw the conclusion that this closes the life 
history of the fungus; that is, that it has lost the perithecia and pycnidia 
stages, as has been supposed true of Botrytis bassii , Isaria strigosa , and 
Oidium lactis , although we are by no means forced to such a conclusion I 
If this is true, we must assume that the spores fall to the ground, sur¬ 
vive the winter among the fallen leaves, and in the spring are carried to 
the leaves by means of the wind or some other agent. This inference 
is supported by the fact that the disease begins nearest the ground. The 
leaves on the lower branches wither first; the upper ones gradually 
follow. On the other hand, it is not conceivable that these delicate, 
thin-walled spores could survive the winter lying upon the damp earth, 
especially since they germinate very readily on the slide upon the ad¬ 
dition of moisture without requiring a resting period. And if these 
were the agents in the penetration of the leaves it is not liKely that all 
