1917] BRUSH—SYCAMORE WOODS 491 
These serve as means of communication between vessels. Large 
transversely elongated, oval, simple pits connect the vessels with 
wood parenchyma fibers (fig. 1, A, sp). 
Tracheids (pl. XXXII, t).—These are numerous and variable in 
form, and all gradations between vessels and wood fibers may’ be 
found. True tracheids have numerous slightly oblique, elliptical, 
or slitlike simple pits (fig. 1, Z, sp) throughout their entire length, 
and at both ends there are many long slitlike openings where they 
overlap other tracheids above and below (fig. 1, E, slp). In addi- 
tion to these pits of the true tracheids most tracheids possess rows 
of slitlike bordered pits and the transverse oval simple pits found 
in vessels (fig. 1, Dand A, sp and bp); hence they somewhat closely 
resemble vessels. Also many of the tracheids have at one or both 
ends a simple perforation (fig. 1, D, p) either with or without bars, 
like those in vessels, in place of the slitlike openings found in true 
tracheids, or else the perforation at the end may be intermediate 
between the slitlike and scalariform types (fig. 1, D, scp). Tra- 
cheids are also found which resemble wood fibers, but these are not 
numerous. They possess, in addition to the oblique simple pits of 
tracheids, the small vertical or often slightly oblique slitlike bor- 
dered pits which characterize wood fibers (fig. 2, D and E, dp). 
These tracheids are usually more or less pointed at both ends and 
sometimes possess small slitlike perforations similar to those found 
in true tracheids (fig. 2, D, slp). 
Wood fibers —These are round, angular, or flattened in trans- 
verse section (pl. XXXII, wf). They are long, slender, and long- 
acuminate at the ends, and are marked by numerous small slitlike, 
obscurely bordered pits* (fig. 2, Eand F, bp). The pits are vertical 
or oblique, often at an angle of 45°, the oblique position being 
greatest in fibers with wide lumina. The ends are sharply pointed 
and often conspicuously forked (fig. 2, G). They vary from 1.39 
to 2.02 mm. in length, with an average of 1.63 mm. The broad 
thin-walled wood fibers, as already described, often show a resem- 
blance to tracheids. 
Wood parenchyma fibers-—These have acute ends, are moder- 
ately thin-walled, and are composed usually of 4~8 individual cells. 
‘The border is hardly visible where the fibers have been isolated by maceration. 
