350 
Journal oj Agricultural Research 
Vol. XXX, No. 4 
week old the cultures of eucalyptus 
root rot, on both maltose and raisin 
agars, quickly developed a number of 
light-brown branching rhizomorphs 
with whitish tips. These extended 
downward and outward from the cen¬ 
tral portion of the mycelial growth. 
The appearance of these structures was 
somewhat varied, but perhaps can be 
described best as at first antlerlike, 
closely resembling the branches of cer¬ 
tain Clavarias. In some cases the 
ends were pointed; in others they were 
blunt and flattened. 
When the cultures of the eucalyptus 
root-rot fungus were 2 weeks old, it 
was noticed that in both those on mal¬ 
tose and on raisin agar the ends of 
some of the rhizomorphs had turned 
upward and had continued growth in 
this position until they reached slightly 
above the surface of the agar. That 
the upward growth of these submerged 
organs was the result of their own 
volition and that they were not de¬ 
flected upward by the walls of the 
flasks were clearly evident. The ex¬ 
posed ends were whitish and at their 
junction with the surface of the agar 
there soon developed outward a downy- 
appressed mycelial growth. In this 
way the growth of the fungus might be 
started anew at several points on the 
surface of the agar in advance of the 
superficial mycelium developed out¬ 
ward from the original point of inocu¬ 
lation. After reaching the surface of 
the agar the rhizomorphs grew but 
little longer. They rarely protruded 
above the surface of the agar more 
than from one-sixteenth to one-eighth 
inch. 
With the increased age of the cul¬ 
tures the rhizomorphs gradually ac¬ 
quired a darker coloring until they be¬ 
came dark brown. When about 4 
weeks old, it was noted on viewing the 
cultures by transmitted light that there 
radiated from many of the rhizomorphs 
a dense but delicate growth of whitish 
mycelium having an opalescent ap¬ 
pearance, like the growth of certain bac¬ 
teria in stab cultures. So dense was 
this halo of radiating mycelial growth 
that its filamentous character could be 
distinguished only at the periphery, 
even with a hand lens. Beginning at 
the ends of the rhizomorphs, or prac¬ 
tically so, this radiating halo of my¬ 
celium gradually became broader, pro¬ 
ceeding away from the end until it 
had attained a length of as much as 5 
mm., measured radially from the 
rhizomorphs. The appearance called 
to mind the root-hair development on 
a radish seedling, except for the fact 
that the radiating mycelial threads were 
much more minute and dense in com¬ 
parison. Other rhizomorphs without 
this root hairlike development of deli¬ 
cate radiating mycelial filaments had 
numerous little white branches from 
1 to 3 mm. long that developed out of 
the old brown rhizomorph at more or 
less of a right angle, like the aerial 
roots along the stem of the English ivy. 
Sometimes there would be one every 
millimeter or two, or a space of several 
millimeters might occur without them. 
In other cases these branches would 
develop in pairs or even in tufts of 
several, some of which were branched. 
Eventually these numerous, short, 
more or less radially disposed lateral 
branches of the rhizomorphs also be¬ 
came brown. This is truly a remark¬ 
able fungus that is well worth an 
intensive cultural study. 
In a number of the cultures in this 
series, chiefly those of the Florida form, 
clusters of mushrooms made their 
appearance after a more or less definite 
period of time and attained a more or 
less perfect stage of development. The 
first evidence of sporophore formation 
was the development of a little group of 
hornlike processes which quickly dif¬ 
ferentiated into a cluster of embryonic 
mushrooms. The time at which fruit¬ 
ing began is based in the tables upon 
the appearance of the latter. In prac¬ 
tically every case the clusters of fruiting 
bodies developed first from the central 
portion, or oldest part, of the culture. 
After one cluster of mushrooms had 
started its development at this point, 
from one to five others sometimes 
appeared, developing beside the first 
one, or at the periphery of the central 
mycelial mass, or at points farther out 
from the central mycelial mass, such as 
the ends of the rhizomorphs which had 
turned upward and reached the surface 
of the agar, or from the mycelial growth 
developed where the ends of the 
rhizomorphs appeared at the surface of 
the agar. As a rule, only the cluster of 
mushrooms first appearing attained full 
development, and only a few of the 
sporophores within this cluster attained 
any great size. In a few cases, how¬ 
ever, a second, and even a third, cluster 
of mushrooms developed in more or less 
rapid succession. The caps were hemi¬ 
spherical at first, but quickly became 
more or less sharply centrally depressed 
or depressed-umbonate as they ex¬ 
panded to their full development. The 
young sporophores presented a consid¬ 
erable variation in color, ranging from a 
creamy white when very young to buff 
or fawn color as they became somewhat 
older. As they approached maturity 
the marginal portion of the pileus 
