280 ANATOMY OF THE GYMNOSPERMS 



3. L. Lyallii, Parl. 



Tamarack. Mountain Larch 



Transverse. Growth rings narrow, variable. The summer wood prominent 

 and dense or sometimes open, equal to about one half to one third 

 the spring wood; the tracheids in regular rows, very unequal, small, 

 radially narrow and rounded. Spring tracheids rather large, squarish- 

 hexagonal, thin-walled, very uniform in regular rows. Medullary rays 

 prominent, not very broad, i cell wide, distant 2-8 rows of tracheids. 

 Resin canals not very numerous, small and widely scattering, devoid 

 of thyloses, the epithelium not very narrow, thick-walled, the nutrient 

 parenchyma obscure or wanting. Resin cells somewhat numerous, 

 slightly resinous and easily distinguished. 



Radial. Rays sparingly resinous throughout, the tracheids rather numerous, 

 marginal, sometimes interspersed. Ray cells very straight through- 

 out, equal to 3-7 spring tracheids ; the upper and lower walls thick, 

 somewhat conspicuously pitted ; the terminal walls coarsely pitted 

 throughout ; the lateral walls with numerous small, oval, distinctly 

 bordered pits with an oblong, narrow orifice, 3-6 per tracheid, in the 

 summer wood abruptly reduced to i. Bordered pits in i row, often 

 in pair's, elliptical, large. Pits on the tangential walls of the summer 

 wood rather numerous but small, and confined to the outermost 

 tracheid wall. Resin cells few, 15 /i, wide, 110-155 /x, chiefly about 

 125 fji, long. 



Tangential. Rays rather numerous, low to high, somewhat resinous. Fusi- 

 form rays very narrow and variable in height ; the narrow' and linear 

 terminals often very unequal ; the cells all thick-walled ; the resin 

 canal small, usually narrow and oblong, often much reduced and 

 nearly obliterated. Ordinary rays more or less 2-seriate in part, 

 narrow, the cells very equal and uniform, narrowly oblong. 



A low, straggling, Alpine tree, rarely exceeding 15 m. in height, with a 

 trunk upwards of 1.50 m. in diameter. 



In the Rocky Mountains of Washington and Montana (Sargent); summit 

 of South Kootenai Pass ; from Cascade Mountain, Bow River Valley, 

 westward ; forming the last belt of timber on all the peaks of the Rocky 

 Mountains, and ranging from 6000 to 7000 feet elevation ; growing with 

 Pinus albicaulis (Macoun). 



4. L. leptolepis, Gordon 



Jap. = Fiijimatsit 



Transverse. Growth rings rather broad. The very prominent and dense 

 summer wood composed of very angular and unequal tracheids in 

 irregular rows ; nearly equal to the spring wood, from which the tran- 

 sition is abrupt. Spring tracheids large, thin-walled, very uniform in 

 regular rows. Medullary rays prominent, i cell wide, distant 2-10 rows 

 of tracheids. Resin passages not numerous, somewhat widely scat- 

 tering, chiefly in the summer wood, the epithelium rather thin-walled, 



