108 College of Forestry 
Microscopically the wood of bitternut hickory presents the 
usual features of the ring-porous type. The growth rings are 
fairly well defined by the zonate arrangement of the large 
vessels in the early wood of the erowth ring and by the 
tangential flattening of the cells on the outer face of the 
late wood. In the late wood the vessels become fewer, 
smaller, and scattered; the larger ones of the early wood are 
characterized by their abundance of tyloses. The wood of 
the bitternut hickory is seen to consist of (a) uniseriate and 
multiseriate pith-rays, (b) pitted vessels, (¢) metatracheal 
zonate wood parenchyma, and (d) wood prosenchyma with 
both simple and bordered pits. The pith-rays, which are 
composed of small, mostly radially elongated, homogeneous 
cells, are irregularly disposed, not uniform in height or shape, 
and vary from one to four, or rarely five, seriate. In the 
beginning of the growth ring the large vessels, or pores, as 
they are termed when viewed in cross section, are scattered 
and never more than two to three rows deep. In the remain- 
ing portion of the growth ring they may be either solitary 
or arranged in radial groups, ‘usually of from two to three, 
or rarely five. Great variation is exhibited in the thickness 
of the vessel walls. The larger vessels in the early wood 
usually have comparatively thin walls with their lumina 
rather densely occluded by tylosal formations. The smaller 
vessels in the late wood as a rule have exceedingly thick walls, 
especially where contiguous. In general it may be stated that 
all solitary vessels have comparatively thin, uniform cell 
walls. The grouped vessels, however, usually have very thick 
walls which decrease in thickness characteristically at their 
distal ends. The walls of contact between two vessels bear 
densely packed and rather large bordered pits, the borders 
sometimes being hexagonal owing to crowding. Where they 
border on the medullary rays the walls of the vessels are fur- | 
nished with simple pits. The scalariform markings charac- 
teristic of yellow birch and sugar maple woods are totally 
lacking in this one. Wood parenchyma occurs abundantly 
but is exceedingly variable as to its distribution. In trans- 
