Nov., 1922] KAUFFMAN AND KERBER HEART-ROT OF LOCUST 507 
disappear." Boyce (1920) notes that in the incense-cedar rot ''hyphae 
were very rare in the pockets of badly decayed wood," although nests of 
mycelium occurred in places. He also notes that hyphae must have been 
present earlier because of the hypha-holes in the cell walls. In the slightly 
decayed wood of the incense cedar hyphae occur abundantly, although 
Boyce states elsewhere that "the line of demarcation between sound and 
decayed wood is very sharp." We have here, then, a situation somewhat 
different from our case in that hyphae occur back of the line of demarcation, 
although they disappear later. Von Schrenk and Spaulding (1909) seemed 
to have little difficulty in finding mycelium of Fomes igniarius *'in the 
completely decayed" wood, where, according to these authors, "the my- 
celium of the fungus is abundant in the large vessels and medullary rays." 
The hardwood host or hosts which were studied are not mentioned, and it 
may be presumed — albeit at some risk — that the matter is a variable and 
that the most frequent condition is not such as they describe. There is, 
furthermore, no doubt that small masses of hyphae do accumulate in nests 
or broken-down cavities and there persist, perhaps because of their bulk. 
The question remains, what happens to the other portions? How do the 
isolated hyphae, responsible for innumerable holes in cell walls, disappear? 
Having exhausted the food, they may die and disintegrate. We may say 
they are resorbed. But this leaves he matter vague, especially as applied 
to the portions near the line of demarcation between the rot and the ap- 
parently sound wood where one would expect dead hyphae to remain 
visible. The idea of dissolving themselves (resorption) by the ferments of 
their own making seems unlikely. One other explanation easily comes to 
mind, viz., that bacteria follow the course of the rot, gaining entrance by the 
same path as the wound parasite, and destroying the mycelium as soon as 
the latter has lost its vigor. At first thought this explanation seems 
plausible. So far, however, no bacteria of wood-destroying ability seem 
to have been isolated. Schmitz (1919), on the other hand, found strong 
indications that certain heart-rotting fungi will destroy more wood in the 
presence of some common and widely distributed bacteria than when these 
fungi function by themselves. Meanwhile the rotten core seems to be 
disintegrating still further through the action of some agent. May not the 
mycelium while still present secrete enough enzyms, which persist actively 
for a considerable time, and which are responsible for the continued dis- 
integration going on in the rotten core? This whole question still has a 
strongly unsolved quality and needs further attack. 
Although the laboratory and field work was done entirely by Mr. 
Kerber, the points were worked out by constant cooperation. The authors 
are under much obligation to Prof. Filibert Roth for the use of the testing 
machine and for assistance in making the tests; and to Dr. W. W. Tupper 
for valuable advice and assistance in the study and staining of the locust 
wood. 
Cryptogamic Laboratory, 
University of Michigan 
