- (1) The large round or oval pores or vessels grouped mostly in
the spring wood first attract attention. Smaller ones, but still quite
distinct, are to be seen scattered all thru the wood. It is by the number
and distribution of these pores that the different oak woods are
distinguished, those in white oak being smaller and more numerous,
while in red oak they are fewer and larger. It is evident that the
greater their share in the volume, the lighter in weight and the
weaker will be the wood. In a magnified cross-section of some woods,
as black locust, white elm and chestnut, see [Chap. III], beautiful patterns
are to be seen composed of these pores. It is because of the
size of these pores and their great number that chestnut is so weak.
- (2) The summer wood is also distinguishable by the fact that, as
with the conifers, its cells are smaller and its cell walls thicker than
those of the spring wood. The summer wood appears only as a narrow,
dark line along the largest pores in each ring.
- (3) The lines of the pith rays are very plain in some woods, as in
oak. [No. 47], Chap. III.
- (4) The irregular arrangement and
- (5) Complex structure are evident, and these are due to the fact that the wood substance consists of a number of different elements and not one (tracheids) as in the conifers.
Looking at the radial section, Fig. 20:
- (6) If the piece is oak, the great size of the medullary rays is
most noticeable. Fig. 32, [p. 37]. They are often an inch or more
wide; that is, high, as they grow in the tree. In ash they are plain,
seen thru the microscope, but are not prominent.
- (7) The interweaving of the different fibers and the variety of
their forms show the structure as being very complex.
In the tangential section, Fig. 20:
- (8) The pattern of the grain is seen to be marked not so much by
the denseness of the summer wood as by the presence of the vessels
(pores).
- (9) The ends of the pith rays are also clear.
In diffuse porous woods, the main features to be noticed are: In the transverse section, Fig. 21:
- (1) The irregularity with which the pores are scattered,
- (2) The fine line of dense cells which mark the end of the year's
growth,
- (3) The radiating pith rays,
- (4) The irregular arrangement and,
- (5) The complex structure.
In the radial section, Fig. 21:
- (6) The pith rays are evident. In sycamore, [No. 53], Chap. III,
they are quite large.
- (7) The interweaving of the fibers is to be noted and also their variety.