202 
indicate a single growth ring; the inner part of the segment of the 
ring which is either more porous or less compact indicates the 
spring wood, while the outer portion which is often less porous 
or more dense is the summer wood; each growth ring is made up 
of both spring and summer wood, the inner part always being 
thespring wood. In some of the pines the spring and the summer 
wood are distinguished from each other as two distinct bands; 
whereas in some woods there is a gradual transition from the 
spring to the summer, and in still other cases there is no apparent 
difference between the two. 
The pith rays always appear as lines of compact wood in the 
Cross section extending at right angles to the growth rings; in 
longitudinal radial section they appear as smooth patches at 
right angles to the parallel bands of the spring and summer wood. 
When the pith rays are very small, wetting the cross section wil] 
often cause them to be more easily seen. 
The pores are small openings usually no larger than that caused 
by the prick of a pin; they are plainly visible with a magnifier on 
a cross section which is clean-cut, in some cases they may be 
seen without the aid of a magnifier. In the Black Locust and 
sometimes in the Thorny Locust these large pores are filled with 
cellulose material. The pores in the summer wood arranged 
radially will be at right angles to the growth rings, whereas those 
arranged concentrically will be parallel to the growth rings. To 
determine a or b of 19 it is always desirable to make as thin a 
Cross section as possible with a sharp knife, hold the section up to 
the light, and by looking through it one can easily determine 
whether or not the cells are arranged in regular rows. 
Resin ducts appear as very small dots in cross section; the sur- 
face of the wood must be clean-cut without any tearing of the 
tissue in order that one may be sure of the presence of the ducts; 
it is usually best to wet the wood after making the section, since 
wetting will cause the duct to be more easily seen. It is usually 
of a lighter color than the surrounding wet tissue. 
The characteristics of odor and of taste can be used to advan- 
tage only after one has handled different kinds of wood; a 
characteristic odor or taste refers to one which is not commonly 
