1917] BRUSH—SYCAMORE WOODS 495 
Gross characters.—In general appearance the wood is similar to 
that of Arizona sycamore, although it is slightly lighter, softer, 
and more durable. Although moderately tough, somewhat cross- 
grained, and rather difficult to split and work, it is relatively weak. 
The heartwood is light brown, slightly tinged with red; the sapwood 
is light yellowish brown. The annual rings of growth are more or 
less clearly defined on a smooth transverse section (pl. XXXIV). 
The pith rays (pl. XXXIV, pr) appear as numerous conspicuous 
thin lines. 
Minute characters.—Vessels (pl. XXXIV, v) are quite evenly 
distributed throughout the annual rings of growth and are grouped 
as in the other two species already described. The beginning of 
each annual ring is marked by a well defined row of slightly tan- 
gentially flattened pores larger than those formed later. They 
measure 0.06-0.09 mm. in diameter and average 0.073 mm. 
(table II). The average length of vessel segments is 0.677 mm., 
varying from 0.61 to 0.75 mm. in length (table III). Tracheids 
(pl. XXXIV, #) do not differ from those in the other two species 
described and show the same transitional forms to vessels and 
wood fibers. Wood fibers (pl. XXXIV, wf) are from 1.26 to 
1.93 mm. long, with an average length of 1.55 mm. (table IV). 
Wood parenchyma fibers and intermediate fibers are in all respects 
similar to those of the other two species (fig. 2, A,B,C). Pith 
rays (pls. XXXIV, XXXVII, pr) are conspicuous in all sections. 
hey are narrowest in this species and have an average width of 
5 cells (0.09 mm.). They are on an average 26 times as high as 
wide, being thus much higher than in the other two species. The 
pith ray cells in the tangential section are round and slightly 
higher than broad. 
Forrest SERVICE 
Wasuincton, D.C. 
EXPLANATION OF PLATES XXXTI-XXXVHI 
PLate XXXII.—Transverse section of wood of common sycamore (P. 
occidentalis), showing parts of two annual rings of growth; ew, early wood; 
lw, late wood; 2, vessels; wf, wood fibers; pr, pith rays. 
