162 ARMILLARIA MELLEA, 
Brefeld found that his older cultures produced a profusion 
of aerial rhizomorphs of the subterranean type. When 
these were growing strongly he dug up some thick roots of 
Scots pine and brought them undamaged and fresh into 
close contact with the apices of the rhizomorphs (* Ich grub 
sie aus und brachte sie unverletzt und frisch mit den Rhizo- 
morphenspitzen in innige Beriihrung’). His figures show 
that the pieces of root were only about 4 in. long. Brefeld 
found that the rhizomorph apices grew into the roots very 
quickly, both through the cut ends and through the un- 
damaged bark. The time that they took to penetrate by 
each route is not stated. 
Now, when digging up fairly thick pieces of root it is 
very difficult not to damage the bark, so that in this experi- 
ment the rhizomorphs may have grown in through wounds. 
Also cut pieces of roots, especially of coniferous roots, 
quickly lose their vitality and even after a very short time 
cannot be described as healthy roots. Brefeld says that 
the rhizomorphs grew in at once (‘sofort ’), but the possi- 
bility is not excluded that the first rhizomorphs to enter 
gained admission through the cut end, whereas the others 
may have taken some days about it. It should not be 
taken, then, as proved that rhizomorphs can force their 
way into a healthy root through undamaged bark. 
The evidence gained from my own observation supports 
the view that the rhizomorphs can only attack through 
damaged or dead roots. Take the following instance. In 
Bagley Wood, near Oxford, a series of quarter-acre experi- 
mental plots were planted in 1907. Various species of 
conifers were used, and my observations, which date from 
1913, show that most of the area is infected with Armillaria. 
At certain points there are large stumps from which rhizo- 
morphs radiate in all directions, and some thousands of 
the toadstools appear annually on and around these stumps. 
The fungus was found in plots containing each of the follow- 
ing species: Corsican pine, Weymouth pine, Norway and 
Sitka spruce, larch, and deodar, and yet, with the exception 
of some fifteen Weymouth pines and a number of Sitkas, 
