328 ANATOMY OF THE GYMNOSPERMS 



simple, oblong, or oval pits, almost strictly i per tracheid, in the 

 summer wood distinctly bordered and then large, oval, with a broad, 

 oblong orifice. Bordered pits large, elliptical, rather numerous, in 

 i row. Pits on the tangential walls of the summer wood wholly 

 wanting. 



Tangential. Fusiform rays rather numerous, medium, narrow, the slightly 

 prolonged terminals composed of a few small tracheids ; the gradually 

 inflated portion composed of very thin-walled cells all broken out. 

 Ordinary rays medium, rather numerous, not very broad and present- 

 ing two principal aspects: (i) low to medium rays composed of 

 i-several oval parenchyma cells with small, terminal tracheids which 

 often become predominant ; and (2) the highest rays with numerous 

 tracheids and few, interspersed parenchyma cells. 



25. P. Murrayana, A. Murr. 



Black Pine. Lodge Pole Pine. Spruce Pine 



Transverse. Growth rings usually broad. Summer wood very thin, the 

 structure very open throughout, the transition from the spring wood 

 very gradual ; the tracheids compressed, unequal, rather squarish, in 

 somewhat irregular rows. Spring tracheids somewhat squarish-hex- 

 agonal, often in very irregular rows, unequal, the walls thin. Resin 

 passages rather small and scattering; the epithelium in i row of very 

 large and thin-walled, somewhat radially flattened, nonresinous cells, 

 immediately inclosed by a layer of large, thin-walled tracheids. Med- 

 ullary rays prominent, broad, i cell wide, numerous, distant 2-9, more 

 rarely 1 1 rows, of tracheids. 



Radial. Rays uniformly somewhat resinous throughout ; the ray tracheids 

 sparingly dentate, more or less reticulate in the summer wood, mar- 

 ginal and interspersed, often predominant. Ray cells apparently of 

 two kinds, but merging so as to be more or less indistinguishable, 

 strongly but variously fusiform ; the terminal walls thin and entire or 

 locally thickened ; the upper and lower walls either entire or locally 

 and irregularly thickened, thin ; the lateral walls with rather small, 

 round, oval, or lenticular pits, at first simple, but toward and in the 

 summer wood with a more or less obvious border and oblong orifice, 

 1-4, rarely 5, per tracheid, in the summer wood reduced to 1-2. Bor- 

 dered pits in i row, sometimes in pairs, not much crowded but strongly 

 elliptical. Pits on the tangential walls of the summer wood wholly 

 wanting. 



Tangential. Fusiform rays low, few and small, rather broad, more or less 

 unequal, acute or somewhat prolonged, the cells rather small and 

 thick-walled throughout, the central tract usually much broken out. 

 Ordinary rays numerous, broad, when a few cells high conspicuously 

 fusiform ; the high rays commonly contracted at the position of small 

 and frequently interspersed tracheids ; the parenchyma cells rather 

 thin-walled, round, or transversely oval, very unequal and variable, the 

 higher rays commonly showing smaller and thicker-walled cells either 

 singly or in pairs. 



