322 ANATOMY OF THE GYMNOSPERMS 



equals the red pine of the east in height and diameter (Macoun) ; south- 

 ward through northern Maine ; at Ferrisburg, Vermont ; thence westward 

 along the southern shores of Lake Michigan to central Minnesota. 

 Barren, sandy soil, more rarely in rich loam (Sargent). 



18. P. contorta, Loud. 

 Scrub Pine 



Transverse. Growth rings thick. Summer wood dense, conspicuous, often 

 exceeding the spring wood ; the tracheids in regular rows, those in the 

 outer portion generally much compressed, variable, those of the central 

 portion more uniform and with rounded lumens; transition from the 

 spring wood gradual. Spring tracheids hexagonal, unequal, in regular 

 rows, the walls rather thin. Resin passages scattering, numerous, 

 small; the epithelium in 1-3 rows of angular, thin-walled cells which 

 merge outwardly into thicker-walled elements, the whole forming an 

 irregular and somewhat extended tract. Medullary rays rather narrow, 

 i cell wide, not prominent, rather numerous, distant 2-12 rows of 

 tracheids. 



Radial. Rays nonresinous ; the tracheids numerous, low, sparingly inter- 

 spersed and sometimes predominant, distinctly reticulated throughout. 

 Ray cells of one kind only and variously fusiform ; the terminal, 

 upper, and lower walls very thin and often much broken out or wholly 

 wanting; the lateral walls with large, oblong, or lenticular pits which 

 often become round or oval when the ray is only i cell high, and on 

 the inner face of the spring wood in all rays, 1-4, chiefly 2-3, per 

 tracheid, in the summer wood greatly reduced in size, shape, and 

 number. Bordered pits in i row, sometimes in pairs, elliptical, 

 becoming much reduced and remote in the summer wood. Pits on 

 the tangential walls of the summer wood wholly wanting. 



Tangential. Fusiform rays not numerous, medium ; the terminals acute, 

 rarely somewhat prolonged, and composed of small tracheids ; the cells 

 of the inflated portion all very thin-walled and generally broken out. 

 Ordinary rays medium, rather numerous, the thin-walled parenchyma 

 cells predominant, commonly broken out so as to leave the ray vacant 

 for nearly the whole height, the tracheids chiefly terminal but occa- 

 sionally interspersed as somewhat narrower and rounded elements, 

 causing local but slight contraction. 



A small, stunted tree 6-9 m. high, with a trunk upwards of .50 m. in diameter. 

 Wood light, hard, strong, brittle, and coarse grained. 



Specific gravity 0.5815 



Percentage of ash residue 0.19 



Approximate relative fuel value 58.04 



Coefficient of elasticity in kilograms on millimeters . . 1585. 



Ultimate transverse strength in kilograms 423. 



Ultimate resistance to longitudinal crushing in kilograms 8868. 



Resistance to indentation to 1.27 mm. in kilograms . . 2382. 

 (Sargent) 



