piiiUPrixK WOODS. 357 
and the wood, in splitting, showi^ a series of fliitings. A moderately 
pronounced spiral or twisted grain is evident in a nninhor of onr woods 
which show a resistance to sniootliing in planing and working. "When 
planed in one direction, portions of the surface are smoothed «nnd certain 
others are ronghened, and v^'hon the operation is reversed, the smooth 
surface becomes roughened an the rough surface is smoothed. This 
irregularity of grain is often noticed in amuguis {KoonJrrsiodcndrori 
pinnatum Ell^.), lauan (Shorea spp.), guijo {Shorea (jnifio Bl.) and 
mayapis (Anisoptem spp.). 
(&) MINUTE ANATOMY. 
Elements. — Tlie elements making np wood are, vessels or trachea^ 
traeheids, wood-fi))ers, pitli-ray cells, and wood parenchyma cells. 
• Trdcliccv] vessels, or pores arc long tuhes extending through the wood 
for sotne distance. Their size, arrangement in rows or scattering, and 
their relation to other elements are of great im])ortjince in the classitlca- 
tion of woods. Large vessels are found in calantas (Toona ^pp.), lauan 
(Shorea spp.), and batitinan (Lngerstroemia hatitinan A^id.) ; very small 
ones in bolongeta (Diospj/ros spp.), calamansanay and mancono (Xan- 
ihostejHon verduyoniantis Xaves). 
Wood-p'bers, — These are long and slender, thick-walled cells, contain- 
ing lignin in their walls. Their abundance and the thickness of their 
walls is usually sufTicient to account for the weight and hardness of the 
wood. 
Traeheids. — These are elongated, tapering cells, not so thick-walled 
as the wood-fibers, of relatively greater diameter, with walls more pitted 
and shorter. 
Pith-rat/ cells, — These are short, prismatic, thln-walled cells containing 
starch grains, resin, or other deposits; they are nearly always with their 
long axes horizontal. 
Wuod parenchyma, — Tliis is formed by thin-walled, prismatic cells, 
with starch or otlier inclusions. The cells are scattered witli more or 
less regularity tlirough the wood; the long axes J>eing vertical. The wood 
parenchyma in some woods is arranged in fine, concentric or wavy, 
broken lines. These arc usually of a lighter color tlum the surrounding 
tissue. 
Piih-rays. — These are usually made up of unlignificd cells and extend 
in a radial direction. 
Resin-canals. — These are passages lined with tliin-walled cells which 
secrete a resin whicli is often found exuding from the cells into the 
central passage, or completely filling it. Kesin-canals are found in but 
few of onr woods; for example, Benguet pine (Pinus insularis Endl.), 
lauan (Shorea spp.), apitong (Dipterocarpus spp.), yacal (Ilopea spp-)> 
tanguile (Shorea pohjsperma (Blco.) Merr.), guijo (Shorea guiso BI.), 
mangachapuy (Hopen neminata Merr.), mayapis (Anisopte.ra spp.). 
