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boundaries of the following types on the photographs: 
Type A - forest with no dieback symptoms 
Type B - trees dead and dying with evidence of 
P. cinnamo mi as the cause 
Type G - symptoms of dieback in the understorey 
but trees not affected 
Type D - scattered deaths of banksia and zaraia 
(cause uncertain) 
üriteria for classification into one or other of 
these types requires some amplification. It has previously 
been mentioned that in the southern jarrah forest there 
exists a considerable variation in the manifestation of the 
disease symptoms. One type, the extent of which did not 
become apparent till interpretation began, was a large area 
in which scattered deaths of banksia or zamia occurred. 
These were apparently random occurrences and were not asso 
ciated with known infections or apparent opportunities for 
infection. Although repeated root sampling failed to prove 
the presence of Phytophthora , their existence over quite 
wide areas was cause forconcern. The cause was regarded as 
uncertain and such areas were classified Type D to identify 
their location for future observation. 
For an area to be classified Type 0 it had to 
both banksia and zamia dying in the area or 
immediate vicinity, except where live specimens of 
one of these species were absent. Blackboy deaths 
in numbers were regarded as definite evidence of 
P. cinnamomi , 
the deaths had to form a pattern and not be merely 
an odd death among a number of healthy individuals, 
for those areas with no susceptible understorey 
present, the decision was based on the above 
evidence at the fringes of the type and the inter 
preters’ field knowledge of this situation. These 
areas are often difficult to classify since the 
lack of susceptible understorey vegetation may be 
due to natural site variation or to a long but 
relatively weak infection by P. cinnamomi such that 
the susceptible understorey had been killed but 
conditions had not been favourable for the jarrah 
to have been seriously affected. 
To be classified as Type B, the area had to show 
symptoms in the understorey as for Type U as well as deaths 
in the jarrah of relatively recent origin (fine branches in 
the crown) . Old deaths and stag-headed trees were often 
attributable to past fire damage or old ring-barking. 
In general, it was found that areas which were 
difficult to classify on the photos were equally difficult 
have: 
(i) 
(ii) 
(ill)