HOW TO TELL THE WOODS 281 
they are present also but too narrow to be seen with 
the naked eye. In the conifers there is another pe- 
culiarity of structure which is helpful in telling one 
wood from another—the size and distribution of “resin 
ducts.” These are spaces between the wood cells into 
which the resin oozes; their presence, size and number 
assist in separating one softwood from another. 
For the purpose of classification all the woods found 
in the United States may be grouped into two classes :* 
I. Non-porous woods containing the coniferous varie- 
ties or softwoods. In this class the pores are absent 
and the limit of the annual ring is marked by the denser 
and usually darker part grown during the summer. 
II. Porous woods containing the hardwoods. This 
class of woods contains more wood elements and the 
growth rings are marked by the presence of large pores 
in the early spring growth and the more compact 
arrangement of the late summer growth—toward the 
outside of the tree. -A cross section of a chestnut log, 
for instance, shows very clearly the difference between 
the spring and summer wood. 
This class of porous woods is further divided into: 
(a) Ring porous woods, where the pores in the early 
wood are large and arranged in a ring or band. Chest- 
nut, oak, hickory and ash belong to this class. (b) 
Diffuse porous woods. Pores numerous but scattered 
through the ring. Mahogany is an example of this kind. 
In some cases the annual ring is made out with diff- 
eulty. 
1The New York State College of Forestry at Syracuse has 
prepared a collection of the most common woods, thirty-one in 
number, and a bulletin deseribing this collection, containing a key 
for their identification. This collection is sent to the citizens of 
the State upon receipt of $.50 for packing, postage, ete. 
