Blister Canker 
11 
liquid and solid media, but found their viability to decrease 
rapidly with age. In tests made soon after maturity of the 
spores an average of 82.2 per cent germination was secured, 
using semi-solid and liquid synthetic media, and water cul- 
tures which contained one per cent each of cane sugar and 
peptone. There was little difference in the amount of ger- 
mination in any of these media. Spores which were placed in 
a moist chamber for a few hours and then desiccated did not 
germinate at all. Spores which had been kept in the labora- 
tory for six weeks gave a germination test of only 8.5 per 
cent. No satisfactory results were obtained from the use of 
solid media. 
Upon germination the endospore gradually draws away 
from the exospore except near the points where the germ tubes 
emerge. Later the exospore is entirely broken up. 
ASCOGENOUS STAGE 
The perfect or perithecial stage of the fungus appears 
one or more years after the conidial stage. Under favorable * 
conditions it appears the following season tho in many cases 
it does not appear at all. The perfect stage is rarely found 
except in cankers on the trunk and large branches. During 
the early spring and summer perithecia are formed in the 
stromata which have previously borne conidia on their sur- 
faces. These perithecia are arranged more or less in layers 
beneath the surface of the stroma, and are 0.2 to 0.4 mm. 
wide by 0.3 to 1.8 mm. long. The older and larger perithecia 
lie near the center of the stroma and are connected with the 
surface by means of long narrow necks. New perithecia are 
formed both above and below the first layer and around the 
edges of the stroma gradually increasing its size. Two or 
more stromata may fuse at the edges forming one very large 
irregular stroma. The asci which are about 12 to 15 by 160 
to 180 microns arise from all parts of the interior of the 
perithecia with their free ends extending diagonally toward 
the center and the neck. Asci of all stages of development 
may be found in the same perithecium. Interspersed among 
the asci are numerous long sterile mycelial threads. The asci 
contain eight oblong brownish-black spores each. These 
spores measure about 10 to 12 by 13 to 16 microns when dry, 
but upon absorbing moisture become almost spherical. 
During wet weather the stromata absorb water readily 
and the spores are expelled in great quantities. Some remain 
clinging to the surface but many are thrown entirely free. 
Glass slides smeared with vaseline and suspended 1% inches 
