126 
Journal of Agricultural Research 
Vol. I, No. 2 
gradually increases in size as the rot progresses. Marked delignifica- 
tion occurs in the tracheids and cells immediately adjacent to the larger 
vessels in which the fungous hyphae are found, but the medullary rays 
and walls of the large vessels are still strongly lignified, as are also the 
numerous tyloses seen in these vessels. The walls of the tyloses were 
punctured in many places by the fungous hyphae. Six to eight inches 
farther down, or 18 to 24 inches behind the advancing line of the rot, 
the rotted wood is soft and spongy to the touch and is of a straw color. 
In this stage the rotted wood consists of partially changed medullary 
rays, some unchanged wood fibers, and vessels with fragments of these 
in various stages of absorption, all strongly permeated with fungous 
hyphae. Some medullary rays are still intact, while others have their 
outer radial cells either partially or entirely delignified and absorbed, 
so that in pulling apart the rotted wood tangentially, the medullary 
rays often pull out, leaving holes in one piece similar in size and shape 
to the rays, while the rays themselves remain attached to the other 
piece of the rotted wood. 
The final stage of the rot differs but little from this condition, since there 
are still portions of all the elements present either unchanged or only 
partially changed. The rotted wood is rather tough and can be bent and 
twisted without breaking if taken in pieces 12 to 18 inches long and 4 or 6 
inches thick. It is rather soft and spongy, but the fungus apparently 
never completely disorganizes the wood, thereby producing hollows. 
On weathering for two or three months the rot in the tops of the stumps 
and in the ends of the rejected butt cuts turns reddish brown and becomes 
firmly agglutinated, a condition so characteristic of this rot that one could 
identify the rot by this feature alone, without the presence of sporophores. 
The rot has no odor. A section through the reddish discolored wood 
shows an abundance of light-brown hyphae. The remnants of the remain¬ 
ing lignified tissues are also colored light brown. In a freshly cut stump 
which had this rot it would be hard to identify the rot in a cross section. 
Even when the wood is split open, there are no very pronounced 
macroscopic characters to distinguish it, like the string and ray stage 
of the rot caused by Polyporus berkeleyi. 
The following is a brief description of the gross appearance of this rot 
caused by Polyporus frondosus , made as soon as the tree was cut. 
The rot seen in a radial longitudinal view consisted of long white lines 
advancing 6 to 10 inches beyond the more completely rotted wood below. 
These lines apparently were caused by the fungous hyphae following the 
vessels in certain annual rings. There was a watery reddish discoloration 
or “soak” about 2 inches in advance of the white lines. The older rot 
was of a light-tan or straw color and with a slight mycelial weft in checks. 
Some 2 to 6 inches below the upper end of the white lines, white downy 
masses of mycelium could be seen by the aid of a hand lens in the large 
spring vessels situated in the white lines. In cross section the rot had a 
