Blister Canker 
13 
At first the hyphae from conidia are rather heavy and be- 
cause of numerous large vacuoles appear abundantly septate. 
The hyhae produced after the cultures were a few days old 
could not be distinguished in any way from hyphae in asco- 
spore cultures. 
It was a simple matter to secure pure cultures from asco- 
spores. The stromata were placed on moist blotting or filter 
paper in the bottom of deep petri dishes which had been ster- 
ilized. When the spores were expelled they adhered to the 
cover in large quantities. The spores were then transferred to 
poured plates. These cultures were usually free from con- 
tamination except for the presence of bacteria. Bacterial 
growth was prevented by acidifying the media with lactic acid. 
Ordinarily the mycelium branches very little when young 
and the hyphae maintain a relatively direct course. Several 
mm. behind the growing tip the older part of the mycelium 
branches profusely. Many hyphae often arise at the same 
point on one or both sides of the main trunk and spread in a 
fan-shaped area over the media. These hyphae are usually 
much smaller than the parent stock. In the older cultures, 
compact masses of mycelium are formed at these points of 
division on which in many instances the writer has found 
conidiophores and conidia. Conidia were first noted in cul- 
tures which were sealed with paraffin and left for several 
months. An attempt made to germinate these spores met 
with failure. It was later found comparatively easy to induce 
cultures to produce conidia by checking growth suddenly or 
by allowing the culture to dry slightly. It was also found that 
the conidia would germinate readily. 
Gloyer^o indicates that the rate of growth of mycelium in 
apple wood was very rapid where the wood had lost a portion 
of its water content, but that no growth was made where the 
wood was sterilized with steam at 15 pounds pressure. He 
attributes this failure of growth to an excess of water caused 
by sterilizing with steam. In the dry wood he secured the 
phenomenal growth of 8 inches thru heartwood tissues in 
seven days, a feat which the author tried in vain to duplicate. 
Wood cylinders 1 inch in diameter were sterilized in mercuric 
chloride for 30 minutes and then washed in distilled water. 
The ends were next trimmed away with a sterilized knife to 
remove any niercuric chloride which remained, dipped in 
alcohol and the alcohol burned away. Others were sterilized 
by steam under 15 pounds pressure. Five sections sterilized 
each way were inoculated at one end and placed in cotton- 
plugged cylinders which permitted rapid evaporation of water. 
