94 HEART-ROT 
always small and are more or less circular in cross-section, 
though they extend to greater length in the longitudinal 
direction. The cross-section has a diameter of 0°1-0'4 mm., 
and covers one to a dozen or more tracheides. The length 
is fairly regular, being 0°5-1 mm. 
These black specks may occur in the spring or summer 
wood, and do not bear any definite relation to each other, 
except that they some- 
+} times appear in longi- 
ta ant Oy tudinal series, with.a dis- 
WH aN Negtaeea Hi} tance of 1 mm. or so 
. between them. Under 
the high power of the 
microscope they are seen 
@ to be composed of dense 
rH Teal masses of hyphae, all of 
\ eres the broader kind, whose 
walls have become more 
than usually thick, and 
dyed with a deep brown 
or black colour similar to 
Brunswick black. The 
hyphae at these points 
branch very freely, and 
on the outskirts of the 
bi are ae specks in the wood of patch they are seen with 
Tenure sauna PE ggomes amare. rounded ends and have 
a tendency to grow in 
fascicles. Sometimes, however, the brown hyphae may be 
seen continuing as colourless hyphae, and in such cases 
the coloration ceases somewhat abruptly at the limit of 
the black patch. These hyphae are presumably the original 
hyphae which were present before the black patch was 
formed, and which gave rise by branching to the rest of 
the hyphae forming that patch ; but, in addition, hyaline 
branches are also sent to the neighbouring tracheides, and 
these may give rise to new black patches after the parent 
ones have disappeared. 
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