PHILIPPINE WOODS. 
357 
and the wood, in splitting, shows a series of flutings. A moderately 
pronounced spiral or twisted grain is evident in a number of our woods 
which show a resistance to smoothing in planing and working. When 
planed in one direction, portions of the surface are smoothed and certain 
others are roughened, and when the operation is reversed, the smooth 
surface becomes roughened as the rough surface is smoothed. This 
irregularity of grain is often noticed in amuguis ( Koordersiodendron 
pinnatum Biigl*) , lauan ( Shorea spp.), guijo {Shorea guiso Bl.) and 
mayapis ( Anisoptera spp.) . 
(6) MINUTE ANATOMY. 
Elements. — The elements making up wood are, vessels or tracheae, 
tracheids, wood-fibers, pith-ray cells, and wood parenchyma cells. 
Trachea ?, vessels, or pores are long tubes extending through the wood 
for some distance. Their size, arrangement in rows or scattering, and 
their relation to other elements are of great importance in the classifica- 
tion of woods. Large vessels are found in calantas ( Toona spp.), lauan 
{Shorea spp.), and batitinan {Lagerstroemia batitinan Yid.) ; very small 
ones in bolongeta ( Diospyros spp.), calamansanay and mancono {Xan- 
tliostemon verdugonianus Naves). 
Wood-fibers. — These are long and slender, thick-walled cells, contain- 
ing lignin in their walls. Their abundance and the thickness of their 
walls is usually sufficient to account for the weight and hardness of the 
wood. 
Tracheids. — These are elongated, tapering cells, not so thick- walled 
as the wood-fibers, of relatively greater diameter, with walls more pitted 
and shorter. 
Pith-ray cells. — These are short, prismatic, thin-walled cells containing 
starch grains, resin, or other deposits; they are nearly always with their 
long axes horizontal. 
Wood parenchyma. — This is formed by thin-walled, prismatic cells; 
with starch or other inclusions. The cells are scattered with more or 
less regularity through the wood ; the long axes being vertical. The wood 
parenchyma in some woods is arranged, in fine, concentric or wavy, 
broken lines. These are usually of a lighter color than the surrounding 
tissue. 
Pith-rays.— These are usually made up of unlignified cells and extend 
in a radial direction. . 
Resin-canals. — These are passages lined with thin-walled cells which 
secrete a resin which is often found exuding from the cells into the 
central passage, or completely filling it. Besin-canals are found in but 
few of our woods; for example, Benguet pine {Pinus insularis Endl.), 
lauan {Shorea spp.), apitong {Dipterocarpus spp.), yacal {II o pea spp.), 
tanguile {Shorea polysperma (Blco.) Merr.), guijo {Shorea guiso Bl.), 
mangachapuy {Hopea acminata Merr.), mayapis {Anisoptera spp.). 
