10 GREENHEART. 
per cent greater than that of English oak. In a smooth transverse 
section (unmagnified) it resembles superficially the wood of palm. _, 
ANATOMICAL CHARACTERS OF THE WOOD. 
- Like a number of other tropical hardwoods, greenheart shows no 
annual rings of growth. The ground mass of the wood is composed 
of small, thick-walled wood fibers arranged in radial rows (transverse 
section). The vessels, plainly visible to the naked eye on a smooth 
transverse surface, are distributed either singly or in pairs arranged 
radially. They are surrounded by several rows of wood-parenchyma 
fibers which under a compound microscope can be distinguished from 
wood fibers by their thin walls. The pith rays are very narrow and 
visible only when magnified. ! 
- The pores (Pl. ITI, v.) are arranged either singly or in pairs, with 
an average feboagie of 0.13 millimeter, and are fafrly constant in 
size throughout the wood. In outline they are either round or ellipti- 
cal, with the greatest diameter in the radial direction, and are fairly 
thick walled. The vessel walls (Pls. III and IV, v.) in contact with 
the pith-ray cells and with wood-parenchyma fibers have numerous 
bordered pits with transitions to simple pits. These are sometimes | 
large and elliptically elongated, a group often resembling scalariform 
(Jadder-like) markings. The partition wall where the vessel seg- 
ments join end to end is wholly absorbed (simple perforation), leay- 
ing an open passage between the segments. The original partition 
wall is at right angles to the axis of the vessel, and each vessel seg- 
ment ends in a small projection which overlaps the next segment 
above and below. The segments of which the vessels are composed 
consist of cells approximately five times as long as wide (0.67 milli- 
meter in length). 
Wood fibers (Pl. II, w.f.) are small in diameter and have such 
thick walls that the lumina or cell cavities often resemble mere dots 
in transverse section. The fibers vary in length from 1.14 to 1.51 
millimeters, with an average of 1.28 millimeters. The pits are sim- 
ple, with very narrow canals. These latter are not visible except in 
transverse section under the high, power of the microscope. | 
Wood-parenchyma fibers (PI. III, w.p.f.) have very thin walls and 
are only sparingly developed, except where they are grouped around 
vessels with which they communicate through the round or trans- 
versely elongated pits mentioned above. The cells composing the 
wood-parenchyma fibers show considerable variation in length. The 
end walls of individual cells are usually at right angles to the long 
axis of the fiber. 
~ Pith rays (PA. IV, p.7.) are usually from 1 to 2 cells wide and 
from a few to 30 or occasionally 40 cells high. Individual ray cells 
