298 BOTANICAL GAZETTE. [Nov., 
spora Bidwellii Sacc. As soon as the berry exhibits any signs of 
the malady, a thin section through the discolored part will show, 
under the microscope, the mycelium or vegetative portion of the 
fungus. This will be found near the surface of the berry and 
will be seen to consist of hyaline, colorless threads or hyphe, of 
very irregular diameter (1-4), much branched and provided 
with more or less frequent septa. The very young branches re- 
mind one by their shape of the haustoria of Peronospora, but 
their position in respect to the cells of the host and their subse- 
quent development reveal their true character. The presence of 
the septa is alone sufficient to distinguish the mycelium of the 
Phoma or Physalospora from that of Peronospora. 
The mycelium traverses the tissues both between and through 
the cells and under its action the latter soon lose their turges- 
cence and their contents turn brown ; they gradually collapse and 
flatten, and the dried pulp remains only as a thin layer of tissue 
in which the vegetative part of the fungus occupies a large part. 
During the earlier stages of the disease the mycelium is most 
abundant near the surface of the berry and here, at frequent 
points, just beneath the cuticle, it makes a condensed growth that 
results in the formation of the perithecia or conceptacles destined 
to contain the spores. At first colorless, the pseudo-parenchyma- 
teus tissue of these conceptacles soon become pale yellow, then 
brown and finally black. The conceptacles themselves are ovoid 
or globular bodies varying in size from 75 to 140s in diameter, 
and in their development they raise and finally burst through the 
cuticle, imparting to the surface of the berry a pimply or punctu- 
lous appearance. At the apex of the exposed part of each con- 
ceptacle there isa minute opening, or osteolum, through which 
the spores escape at maturity, 
The microscope reveals the fact that the conceptacles are of 
two sorts—pycnidia and spermagonia—names determined by the 
character of their contents, otherwise they do not differ except 10 
size, the pycnidia being the larger, 
NIDIA.—A_ cross-section of a pycnidium shows first a 
clear zone lining the cavity, consisting of very delicate tissue that 
gives rise to the short and thin walled threads, the basidia, upon 
Which are borne the spores, in this case called stylospores, that 
completely fill the remaining portion of the cavity. Thes 
stylospores are one-celled, round or somewhat oblong, being 18 
their longest diameter about 8». Under an amplification of 500 
diameters the cell wall is clearly discernible, the contents having 
ee ‘Viala and Ravaz, “‘ Memoire sur une nouvelle maladie de la vigne, Le Black Rot,” P 
