94 
IOWA ACADEMY OF SCIENCES 
the medullary rays. The interior of the wood has a translucent appear- 
ance owing to the deposition of a large amount of resin. The fungus 
mj-celiiim causes an extra cell proliferation especially well marked 
where the disease has been of long standing. In this case the diseased 
portion may be much larger than the stem below and above. The cell 
walls of the cortex except the strengthening elements do not give the 
lignin reaction but the walls of the tracheids respond readily to lignin, 
they have not therefore altered visibly. In many respects the patholo- 
gical changes are similar to those described for Peridermium pini-cor- 
ticola by Hartig. 
“Wherever the mycelium obtains access, the starch-grains and other 
cell-contents disappear, their place being taken by drops of oil of tur- 
pentine, which form on the inside of the walls or saturate the wall- 
substance itself. The cells are, of course, killed, death however being 
unaccompanied by browning of the tissues. The whole stem, to a depth 
of some three or four inches, is completely saturated with resin, a sec- 
tion of wood, as much as one or two inches in thickness, being more 
or less translucent.” 
“Each year the mycelium spreads from the diseased part into adjoin- 
ing tissues, the rate of progress being usually somewhat more rapid 
longitudinally than horizontally. In proportion as the mycelium spreads, 
so in the passage of the plastic materials confined to the sound side of 
the tree, in consequCxi^e v.hich the cambium in that region is stimu- 
lated to such a degree of activity as to produce exceptionally broad annual 
rings.” 
The following is Peck’s original description of this fungus: 
Peridermium cerebrum. Peck. 
“Peridia large, convex, erumpent, irregularly confluent, forming brain- 
like convolutions, white, rupturing irregularly, the cells granulose, 
radiate-striate on the margin; spores variable, ovate elliptical or sub- 
globose, rough, yellow, .0008' to .0011' long. 
Trunks and branches of young pines, Pinus rigida. Center. May. 
This fungus forms excrescences from half an inch to two inches in 
diameter on the trunks and branches. On the smaller branches the 
excrescence puffs out equally on all sides of the branch. The outer bark 
comes off in large scales, revealing the bright yellow fungus which has 
produced the unseemly s’velling. 
This plant was first detected by Mr. J. A. Eintner, who brought me 
specimens and made known its locality.” 
Manner of Infection. This could not be determined for this spe- 
cies, nor has it been determined for the allied P. pini corticola. It may 
be through an abrasion of the cortical tissue induced by insects or by 
mechanical injuries. A study of the material at hand indicates that 
infection takes place during the early stage of the development of the 
plant branch, during the Ihst year of growth. 
Genetic Connection. The spores mature during the latter part of 
July and presumably infect some other host plants. The European Peri- 
dermium pini corticola is connected with Gronartium asclepiadeum 
