[Vor. 1 
246 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
also found that for the parasitie fungi tested, concentrations of 
from 0.1 per cent to 0.6 per cent were sufficient to retard growth. 
While the mere presence of considerable tannin may not entirely 
prevent the development of a fungus, it may retard its growth, 
and in the mesquite may explain the comparative immunity of 
the wood parenchyma to its attacks. The selective destruction 
of the wood fibers will serve to distinguish this form of decay 
from the other types of hardwood decay. 
From the material found it was not possible to judge of the 
ultimate stages of the disease. In view of the fact, however, 
that sporophores four years old were observed, it seems that the 
resistance of a part of the wood structure is more or less per- 
manent. Хо mesquite trees were found broken off as a result of 
the action of the fungus. It is conceivable, however, that very 
severe storms might break off trees weakened by the disease. ` 
The fungus which causes the decay is Polyporus texanus (Mur- 
rill) Saec. & Trott. The sporophores, which are annual and 
very distinet and easily recognized, develop around old knots. 
At the end of one year the sporophore dries and cracks (pl. 6 
fig. 1, and pl. 7 figs. 1, 2), and many of them become badly eaten 
by inseets. Тһе latter may completely destroy the fruiting 
structure, thereby preventing the formation of new pilei from 
the original one. Тһе sporophores occur either singly or in 
groups. In the latter case the oldest sporophore of the group 
is situated near the trunk, and gives rise during the second year 
to another pileus; from the latter a third one may grow out 
during the following year. This habit is well shown in pl. 6 fig. 
1, and in pl. 7 fig. 1. The photograph reproduced in pl. 6 fig. 1 
shows а group of three sporophores from below ; the oldest one 
(in the back), dried and cracked; the second one formed immedi- 
ately below the oldest one; and the youngest one developed at 
the side. "This condition is also evident in pl. 7 figs. 1,2. On 
the trees observed there was usually only one sporophore or a 
single group of sporophores, and while the internal decay ex- 
tended in some cases for ten to twelve feet up and down in the 
trunk, in no case did the sporophores develop at more than one 
point. 
Polyporus texanus (Murrill) Sacc. & Trott., was first described 
by Murrill (9) in 1904 from a specimen collected by Under- 
