No V.J 1922] KAUFFMAN AND KERBER HEART-ROT OF LOCUST 
499 
Study of the Elements of the Normal Black Locust 
Black locust normally has very little sapwood, this in most cases being 
only three to four rings in width. This sapwood is of a whitish to a pale 
lemon color and is in decided contrast to the golden brown of the heartwood. 
It is a ring-porous hardwood, that is, there is a distinct variation in the size 
of the spring line of vessels as compared to those of the summer wood, as 
seen in cross section. These vessels in the heartwood are filled with tyloses, 
which fact makes locust one of the choice woods for tight cooperage stock. 
The tyloses are also supposed to act as a protection against the invasion 
of disease. The vessels are of the very highest types, having simple end- 
wall pits and spiral vessel markings. The tracheids also have spiral wall 
thickenings, but these are of the tertiary type. It may be mentioned in 
this connection that the tertiary thickenings of the spiral walls of the 
tracheids resemble the hyphae of Trametes rohiniophila so closely that no 
attempt was made to find hyphae in the tracheids. 
Wood parenchyma is found only surrounding the vessels in Rohinia 
Pseudo- Acacia. This fact marks the wood as vasicentric wood — one of the 
highest of the hardwoods. The wood-parenchyma tissues are cellulose and 
stand out clearly when a haematoxylin stain is used. The cell walls are 
comparatively thin, and the pits are simple when communicating with the 
ray cells. 
The fibers are of two kinds: 
1. Lihriform Fibers. These are called mucilaginous fibers in black 
locust. Jeffrey says (The anatomy of woody plants, pp. 33, 34) : 
In these elements the inner portion of the wall has become more or less completely 
modified into a mucilaginous state which causes it to stain strongly with haematoxylin. 
The presence of fibers of this description is often of value from the hygroscopic quality 
imparted to the wood, which prevents undue shrinking or swelling. These numerous 
mucilaginous fibers made the wood particularly valuable for tree-nails in the days of the 
construction of wooden ships. 
2. The second kind of fiber present in black locust is the ordinary wood 
fiber, with a thick wall composed of lignin. These fibers are the principal 
source of strength, hardness, and toughness in broad-leaf woods. Their 
function is principally a mechanical one. In Robinia, they are in rather 
large, compact masses in the late wood, separated by groups or bands of 
pores and parenchyma. 
The ray cells and wood parenchyma are the only living tissues in the 
heartwood of the locust, and even these too become lignified after a time. 
Lignification of the ray cells is common in the early stages of heartwood 
transformation. The ray cells of locust belong to the diffuse type of ray, 
for they have more than one layer of ray cells. They are filled with living 
tissue, mostly containing starch, and give a cellulose reaction with the 
proper stain. The ray cells are storage cells for food and help in the dis- 
tribution of water in the horizontal plane of the tree. The ray cells have 
