436 
B. B. HIGGINS 
Besides the studies on the life history of these forms, it seems best to 
report at this time certain observations on the occurrence of spermatia and 
the development of the ascocarps in several other species. Because of the 
desirability of recording all observations on the details of morphological 
development and on parasitism, each species will be considered inde- 
pendently, before taking up a general discussion of the occurrence and 
function of spermatia. 
Sphaerella BoUeana n. sp. 
Cercospora BoUeana (Thum.) Speg. is very common and widespread 
as a parasite on the leaves of the fig, Ficus carica L., producing small, 
irregular brown spots two to five millimeters broad. When infection be- 
comes very abundant distinct spots are not formed, but the whole under 
surface of the leaf becomes covered with the dark olive-brown conidiophores 
and the leaf soon drops from the tree. 
The development of the spots is very slow and irregular; and this, with 
the fact that conidiophores may often be found on the lower surface before 
a distinct spot is discernible above, suggested that the leaf tissue is killed, 
not by the direct action of the fungus but by the drying of the tissues 
through the epidermis broken by the emerging conidiophores. In view of 
the fact that most parasitic species of this genus kill the host tissue rapidly, 
apparently by means of some poison secreted by the fungous mycelium, 
some study was made of the development of the spots and of the relation 
of the mycelium to the leaf tissue. 
The results from many artificial inoculations show that about a month 
is required for a typical leaf spot to form. Infection seems to take place 
through the stomata, since placing the spores on the upper surface of the 
leaf failed to produce infection ; though the actual entrance of the germ tube 
has not been observed. The first sign of disease is a browning of the epi- 
dermal cells at the point of infection, which begins to appear in from five to 
ten days. By the end of two to three weeks, tiny brown spots also begin 
to appear on the upper surface. These gradually enlarge and coalesce 
until a fully developed spot is formed. 
Microscopical examination of sectioned and stained material showed the 
reason for this peculiar feature. The mycelium grows very slowly and is 
mostly intracellular. The host cells actually penetrated are killed; but, 
for a time, the adjoining cells seem to suffer very little injury. Evidently 
some poisonous substance is produced; but it is of such a nature that it 
does not diffuse rapidly from cell to cell. Very often the hyphae enter the 
vascular bundles and spread much more rapidly, sending out branches 
through the pits in the vessels and killing the surrounding cells. The 
hyphae are slightly constricted on passing through a cell wall, and do not 
disintegrate the walls to any appreciable extent. 
