1917] BRUSH—SYCAMORE WOODS 487 
WOOD PARENCHYMA FIBERS 
Wood parenchyma fibers, used for the storage of food materials, 
are usually less than half the length of the wood fibers, are moder- 
ately thin-walled, and composed of a number of individual cells. 
In sycamore woods wood parenchyma fibers occur only in the 
neighborhood of vessels and pith rays, from which they obtain their 
food supply. Each fiber consists of 1-8 oblong or cubical cells. 
Two forms of wood parenchyma fibers may be distinguished in 
sycamore wood. The fibers of the first form communicate directly 
with the vessels and have large transverse simple pits (fig. 2, A). 
The fibers of the second form communicate with one another and 
with those of the first form, but they do not communicate directly 
with the vessels; these have dotlike bordered pits (fig. 2, B). 
INTERMEDIATE FIBERS 
Intermediate fibers, although very similar to wood fibers, also 
serve for food storage. They are slightly thinner-walled and shorter 
than the latter and possess many small oval oblique bordered pits. 
They may be distinguished from the wood fibers, among which 
they are sparsely scattered, by the starch contained in them. 
They are intermediate in form and function between wood paren- 
chyma fibers and wood fibers; hence the term “intermediate fiber.” 
PITH RAYS 
The three species of sycamore woods may be distinguished from 
each other by the pith rays. The rays of common sycamore are 
much broader in tangential section (pl. XXXV, pr) than those of 
the other two species. They have an average width of 14 cells, 
and the ratio of width to height is 1:5. The rays are narrowest in 
the California sycamore (pl. XXXVII, pr); they average only 5 
cells wide, and the ratio of width to height is 1:26. The rays 
in Arizona sycamore (pl. XXXVI, pr) average 8 cells wide, and 
the ratio of width to height is 1:12. In all species the pith rays 
abruptly widen in transverse section at the boundary of each 
annual ring of growth (pl. XXXIII, pr). The pith ray cells as 
seen in radial section are usually much longer than they are high, 
