34 ANDERSON: DASYSCYPHA RESINARIA 
pruned branches of the lower part of the trunk. At these places 
the spores gain access to the living inner bark and to the cambium, __ 
where they germinate and cause the increased growth of the 
wood and secondary cortex. Wounds caused by insects and by — 
hail and by the breaking of the branches by snow and ice, also 
expose the cambium to the fungus spores. 
Explanation of Plates 1 and 2 
Fic. 1. Dead branch from affected tree, with canker swelling at a2, completely 
surrounding the branch. Ascomata (not visible in the figure) are present only on the 
hypertrophied bark of the canker, ™% natural size. : 
Fic. 2. Portion of affected trunk with three canker swellings; a, dead branch 
around which a small canker has formed and at the base of which the infection took a 3 
place; a’, dead branch with older canker which has spread almost around the trunk; 
6, hypertrophied bark, consisting mainly of the secondary cortex, 1% natural size. 
Fic. 3. Magnified portion of bark, at canker, with unopened ascoma at 4, and 
mature one at 4; at a and ¢ is shown a drop of exuded and hardened resin, >< 30- 
Fic. 4. Section of ascoma, > 30. 
Fic. 5. Section of ascoma through hymenium and sterile portion; @, hymenium; 
6, hypothecium ; ¢, medullary portion of excipulum; d, extal layer of excipulum; ¢, 
pili, X 450. 
Fic. 6. Portion of cup with pili forming the fringe around the disc; a, particles of © 
excreted calcium carbonate with which these hairs are dotted over, & 125. 
Fic. 7. Cross section of stem, through canker; a, resin vesicle in primary cortex, 
larger than normal ones on opposite healthy portion of stem; 64, two chains of patho- ay 
genic resin-canals; c, resin-pocket formed where cambium had been killed; filled 
with hardened resin, & 1%. 
Fic. 8. Section through portion of canker; a, resin vesicle of greater diameter 
than normal ; 44, two chains of pathogenic resin-canals, one in fall and the other in 
spring wood of the following year, < 15. 
Fic. 9. Part of cross section of apparently healthy wood, 6 centimeters below the a 
canker spot; a, pathogenic resin-canals; 4, ‘‘resin cells,’’? lumina of which are filled 
with hardened resin, > 160. 
Fic. 10. Part of cross section of wood at canker, with pathogenic resin-canals (4) 
and ‘‘resin-cells’’ (4), < 160. 
Fic. 11. Tangential section through a chain of pathogenic resin-canals ; ¢, wound 
parenchyma; 4, lining cells of resin-canals; ¢, medullary rays, 160. 
