KEY TO CONIFEROUS WOODS. 65 



6. Heartwood purplish to brownish red; sapwood yellowish white; wood 

 soft to medium hard light, usually with aromatic odor . (No. 6) Red cedar. 

 c. Heartwood maroon to terra cotta or deep brownish red; sapwood light 

 orange to dark amber, very soft and light, no odor; pith rays very dis- 

 tinct, specially pronounced on radial section (No. 7) Redwood. 



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

 yellowish brown. 



a. Odorless and tasteless (No. 8) Bald cypress. 



h. Wood with mild resinous odor, but tasteless (Nos. 1-4) White cedar. 



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



cut (No. 5) Incense cedar. 



B. Resin ducts present. 



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



(Nos. 33-36) Spruce. 



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 (Nos. 18-21) Soft pines. 1 



b'. 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 (Nos. 22-32) Hard pines. 1 



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), 



(No. 37) Douglas spruce. 



b'. Color of heartwood light russet brown; of sapwood yellowish 

 browu; resin ducts very few, irregularly scattered (tracheids without 

 spirals) (Nos. 16 and 17) Tamarack. 



The Norway pine, which may be confounded with the shortleaf pine, can be dis- 

 tinguished by beiug much lighter and softer. It may also, but more rarely, be 

 confounded with heavier white pine, but for the sharper definition of the annual 

 ring, weight, and hardness. 



The lougleaf pine is strikingly heavy, hard, and resinous, and usually very regu- 

 lar 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, pro- 

 posed 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/', resinosa. 



b. Three to six simple pits to each tracheid, on the walls of the cells of the 

 pith ray. — Group 2. P. taeda, palustris, etc., including most of our "hard" 



and "yellow " pines. 

 Section II. Walls of tracheids of pith ray smooth, without dentate projections. 



a. One or two large pits to each tracheid on the radial walls of each cell of the 

 pith ray. — Group 3. P. strobus, lambertiana, and other true white pines. 



b. Three to six small pits on the radial walls of each cell of the pith ray. 



Group 4. P. jiarryana, and other nut pines, including also P. baJfouriana. 



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



3521— No. 10 5 



