8 CONTROL OF THE CHESTNUT BARK DISEASE. 
bark itself, but the pustules show in the eracks and the bark often 
sounds hollow when tapped. After smooth-barked limbs or trunks 
are girdled the fungus continues to grow extensively through the 
bark, sometimes covering the entire surface with reddish-brown 
pustules (fig. 4). These pustules produce mostly winter spores 
(ascospores), although occasionally the long strings of summer spores 
(fig. 3) are also produced, even on bark that has been dead at least 
a year. 
Fic. 4.—Dead chestnut bark showing pustules of the parasitic fungus bearing winter 
spores. 
After a branch or trunk is girdled, the leaves change color and 
sooner or later wither. Such branches have a very characteristic 
appearance and can hardly be mistaken for anything else, except in 
certain localities where the work of twig-girdling insects may pro- 
duce a similar appearance in the spring. In case the girdling by 
the fungus is completed late in the season, the leaves of the follow- 
ing spring assume a yellowish or pale appearance and do not develop 
to their full size (fig. 2). Tf the girdling is completed between spring 
and midsummer the leaves may attain their full size and then turn 
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