MARSHALL: COMBATING INFECTION IN TREES 
37 
careful inspection of both ornamental and roadside tree shows that the 
remedial measures, excellent as they are, have only been commenced. 
Broken branches, open crotches, and splintered wood abound. Roots 
have been broken and torn loose from the soil. Trees have been racked 
and twisted by the wind. Such injuries, even where they are slight, 
tend to open the bark. This natural armor of the tree no longer pro¬ 
tects its wearer with an impregnable coat. The exposed wood is vul¬ 
nerable to attack by harmful fungi. Even under normal conditions 
wood-rotting organisms constitute a serious tree problem. Therefore 
it is highly important that we do all that is possible to guard our trees 
against infection to which they are now dangerously exposed. 
Wood-rotting fungi are legion and varied. Most of them belong to a 
group called the “Basidiomycetes.” Some of their best-known types of 
fruiting bodies are popularly referred to as “mushrooms” and “toad¬ 
stools” when umbrella-shaped, and as “punks” and “conks” when 
bracket-shaped. Such fruiting bodies discharge myriads of spores, 
which are carried by the wind to open wounds where they start new 
infections. Certain of these fungi do not confine their fruiting to the 
normal growing season of the deciduous plants. On the contrary, 
their spores may be discharged in winter as well as in summer. 
The hurricane occurred at the season when the deciduous tree is least 
able to protect itself from infection. This is because the formation of 
callus does not take place during the dormant season, nor is there any 
appreciable plugging of the wood vessels by wound gums and tyloses, 
when the tree is not in a growing condition. Until next spring, wounds 
will remain unprotected by callus and unsealed by natural plugging, 
except in the case of such trees, particularly the conifers, as exude pitch 
or gum to form a natural wound dressing. 
We are then faced with the problem of protecting the trees against a 
really serious threat, even though the wounds themselves may seem of 
minor importance. Immediate treatment of these injuries may prevent 
great damage to our trees in years to come. Although, of course, no one 
can prophecy exactly what the results will be, it certainly appears easier 
to take measures for preventing infection than to check wood-rot after 
it has become established. 
Smoothing to remove jagged wood and particularly the exercise of 
care, when removing broken branches, to make flush cuts which do not 
leave any parts isolated from lines of sap flow, are essential to preventing 
infection. Although small wounds can become infected, it is generally 
