AMERICAN WOODS. 101 



1. NoNpimor^ Woods. 



(Includes all comiVrous woods.) 

 A. Resin ducts wanting. 1 



1. No distinct heart wood. 



a. Color effect yellowish white; summer wood darker yellowish (under microscope pith ray without 



trachei ds ) Firs. 



b. Color effect reddish (roseate) (under microscope pith ray with tracheids) Hemlock. 



2. Heartwood present, color decidedly different m kind from sap wood. 



a. Heartwood light orange red ; sapwood pale lemon ; wood heavy and hard Tew. 



b. Heartwood purplish to brownish red; sapwood \ellowish white; wood soft to medium hard light, 



usually with aromatic odor Bed cedar. 



c. Heartwood maroon to terra cottaor deep brownish red; sapwood light orange to dark amber, very soft 



and light, no odor ; pith, rays very distinct, specially pronounced on radial section Redwood. 



3. Heartwood present, color only different in shade from sapwood, dingy-yellowish brown. 



a. Odorless and tasteless Bald eyjwess . 



b. Wood ^ ith mild resinous odor, but tasteless White cedar. 



c. Wood with strong resinous odor and peppery taste when freshly out Incense cedar. 



B. Resin ducts present. 



1. No distinct heartwood ; color white ; resin ducts very small, not numerous Sjwuce. 



2. Distinct heartwood present. 



a. Resin ducts numerous, evenly scattered through the ring. 



a'. Transition from spring wood to summer wood gradual; annual ring distinguished by a fine line of 

 dense summer-wood cells; color white to yellowish red; wood soft and light Soft pints. 2 



?/. Transition from spring wood to summer wood more or less abrupt; broad bands of dark-colored 

 summer wood ; color from light to deep orange; wood medium hard and heavy Hard pines. 2 



b. Resin ducts not numerous nor evenly distributed. 



a'. Color of heartwood orange-reddish; sapwood yellowish (same as hard pine) ; resin ducts frequently 

 combined in groups of 8 to 30, forming lines on the cross section (tracheids with spirals), 



Douglas spruce. 



b'. Color of heartwood light russet brown; of sapwood yellowish brown; resin ducts very few, irregu- 

 larly scattered (tracheids without spirals) Tamarack. 



ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP. 



Spruce is hardly distinguishable from fir except by the existence of the resin ducts, and microscopically by the 

 presence of tracheids in the medullary rays. Spruce may also be confounded with soft pine, except for the heart- 

 wood color of the latter and the larger, more frequent, and more readily visible resin ducts. 



In the lumber yard, hemlock is usually recognized by color and the slivery character of its surface. Western 

 hemlocks partake of this last character to a less degree. 



Microscopically the white pine can be distinguished by having usually only one large pit, while spruce shows 

 three to five very small pits in the parenchyma cells of the pith ray communicating with the tracheid. 



The distinction of the pines is possible only by microscopic examination. The following distinctive features 

 may assist in recognizing, when in the log or lumber pile, those usually found in the market: 



The light straw color, combined with great lightness and softness, distinguishes the white pines (white pine 

 and sugar pine) from the hard pines (all others in the market), which may also be recognized by the gradual change 

 of spring wood into summer wood. This change in hard pines is abrupt, making the summer wood appear as a 

 sharply defined and more or less broad band. 



The Norway pine, which may be confounded with the shortleaf pine, can be distinguished by being much 

 lighter and softer. It may also, but more rarely, be confounded with heavier white pine but for the sharper defini- 

 tion of the annual ring, weight, and hardness. 



The longleaf pine is strikingly heavy, hard, and resinous, and usually very regular and narrow ringed, showing 

 little sapwood, and differing in this respect from the shortleaf pine and loblolly pine, which usually have wider 

 rings and more sapwood, the latter excelling in that respect. 



The following convenient and useful classification of pines into four groups, proposed by Dr. H. Mayr, is based 

 on the appearance of the pith ray as seen in a radial section of the spring wood of any ring: 

 ►Section I. Walls of the tracheids of the pith ray with dentate projections. 



a. One to two large, simple pits to each tracheid on the radial walls of the cells of the pith ray. — Group 1. 



Represented in this country only by P. rebiuosa. 



b. Three to six simple pits to each tracheid, on the walls of the cells of the pith ray. Group 2. P. taeda, palustrie, 

 etc., including most of our "hard" and "yellow" pines. 



1 To discover the resin ducts a very smooth surface is necessary, since resin duets are frequently seen only with 

 difficulty, appearing on the cross section as fine whiter or darker spots, normally scattered singly, rarely in groups, 

 usually in the summer wood of the annual ring. They are often much more easily seen on radial, and still more so 

 on tangential sections, appearing there as fine lines or dots of open structure of different color or as indentations or 

 pin scratches in a longitudinal direction. 



2 Soft and hard pines are arbitrary distinctions and the two not distinguishable at the limit. 



