DISEASES OF TAXODIUM AND LIBOCEDRUS. 57 
and believes that it consists of decomposition products of 
wood exposed to the disintegrating influences of the outer 
air. These products are dissolved by water and penetrate 
far into the tree, bringing about the characteristic phe- 
nomena of wound rot. Frank * claims that Hartig has 
mistaken the nature of this substance, which he says is not 
a humus compound but wound gum, which acts as a pre- 
servative. A comparison of Hartig’s figure and the one 
on Pl. 4, fig. 4, will show that in point of appearance the 
substance described by Hartig and the one in Taxodium 
cells are alike. I have also found such substances in 
wounds, and neither these nor the substance in Taxodium 
are the wood gum which Frank describes. I believe that 
Hartig is right when he calls them humus solution, but 
cannot agree that they are active in promoting decomposi- 
tion. It might be added that Willkomm f ascribes the 
brown coloration of diseased pine wood to a humus com- 
pound which he says is formed from the cell-walls when 
they begin to decompose. 
No substance corresponding to Frank’s wound gum could 
be obtained from the Taxodium. An aqueous extract of the 
sound wood is yellowish in color, due to some coloring 
matter akin to curcumin. A number of analyses made 
of diseased wood failed to give any substances which might 
be regarded as preservative. The sole difference so far found 
between the normal wood and the diseased wood was the 
constant presence of the humus compounds described in 
the diseased wood. 
There are numerous instances which illustrate the preserva- 
tive and antiseptic properties of humus compounds. The 
preservative powers of peat deposits are well known. Peat 
is largely if not entirely composed of humus compounds of 
one kind or another. Its preservative and antiseptic prop- 
* Frank, B. Krankheiten der Pflanzen 1:32. 1895. 
+ Die mikroscopischen Feinde des Waldes 68. 
35 
