1914) 
VON SCHRENK—A TRUNK DISEASE OF LILAC 255 
grow in the hole, rapidly spreads up and down in the heart- 
wood, and soon grows out from the center toward the bark. Ав 
the disease progresses, the wood is converted into a soft, pithy, 
white mass, having the consistency of corn-stalk pith. Тһе 
line of demarcation between the sound and completely destroyed 
wood is very sharp (see pl. 9), resembling in this respect the 
type of decay caused by this same fungus in living catalpa trees 
((5), pl. 26). Тһе line between sound and decayed wood is so 
sharp that entirely decayed fibers adjoin perfectly sound ones. 
Between the wholly unaffected wood and the completely de- 
stroyed fibers, is a narrow ring of darker wood, which is, to all 
intents and purposes, sound; the wood cells are partially invaded 
by the mycelium of the fungus, and the lumina are filled with a 
yellow-brown liquid, which when seen in mass gives the section 
the dark color referred to. This liquid dries out in some places 
and leaves а brown amorphous substance, such as has frequently 
been found in the early stages of decomposition of hardwood 
wood fibers (6). It probably consists of decomposition products 
which are infiltrated into the sound wood immediately in ad- 
vance of the fungus. In cases where the fungus starts in several 
centers, rings of the darker colored wood surround each decayed 
portion, à condition which is well shown in pl. 9 figs. 1, 2, where 
the fungus is growing in the center of the trunk and in addition 
in three more peripheral localities. In the lilae the brown sub- 
stance referred to is ultimately destroyed (see the middle trunk 
of the lower tier, pl. 9 fig. 2, where the wood is destroyed up to 
the bark). | 
The completely decayed wood, which readily absorbs water, 
resembles pith, and in general is very similar to catalpa wood 
destroyed by Polyporus versicolor (5). It has some of the 
attributes of wood, i.e., it can be split, is fairly compact, and 
cannot be crumbled into powder. Sound lilac wood is very 
heavy and hard, and is composed almost wholly of very thick- 
walled wood cells, with small vessels scattered with considerable 
regularity throughout the annual ring; wood parenchyma is 
almost wholly absent. Тһе hyphs of Polyporus versicolor 
attack and very rapidly destroy the layers of secondary thick- 
ening of the wood cells. The middle laraell: retain the nature 
of lignified fibers and resist destruction almost entirely, although 
