JUNIPERUS 247 



2. J. nana, Willd. 



Common Juniper 



Transverse. Growth rings very variable and unconformable, the tracheids 

 very small throughout. Summer wood thin, of 3-6 tracheids, rather 

 open, often double, the transition from the spring wood gradual. 

 Spring wood broad, the tracheids squarish-hexagonal, not very uni- 

 form, small, the walls medium, the general density varying greatly in 

 different rings. Medullary rays inconspicuous, i cell wide, distant 2-10 

 rows of tracheids. Resin cells numerous, prominent, distinctly zonate. 



Radial. Rays very sparingly, if at all, resinous throughout, wholly devoid 

 of tracheids. Ray cells variable in height, chiefly straight or becom- 

 ing contracted in the summer wood, equal to 7-8 spring tracheids ; 

 the upper and lower walls thin, with broad, unequal, and usually 

 rather distant pits ; the terminal walls thin, often curved, entire or 

 locally thickened ; the lateral walls with large, very prominent, oval 

 pits with an obscure and unequal border, 2-4, or in the summer wood 

 2, per tracheid. Bordered pits numerous, large, as broad as the tra- 

 cheid, in i row. Pits on the tangential walls of the summer tracheids 

 numerous, large, and open. Resin cells 20 /A wide, about 165 p. long. 



Tangential. Rays rather numerous, low to medium ; the cells equal, rather 

 uniform and oblong, sometimes oval, the walls thin. 



Of uncertain range in the northern parts of the continent ; Lake Mistas- 

 sini ; the Shickshock Mountains, Gaspe; Bow River, Alberta; Rocky 

 Mountains from Silver City westward to the summit of the Selkirks in 

 latitude 51; also the south and north Kootenay passes (Macoun); 

 Labrador southward to Massachusetts and New York, thence westward 

 to Michigan, Colorado, and Utah (Britton). 



3. J. rigida, Sieb. et Zucc. 

 Jap. = Muro 



Transverse. Growth rings broad, the structure rather open throughout. 

 Summer wood very thin, of 3-4 tracheids, the transition from the 

 spring wood rather gradual. Spring tracheids conspicuously hex- 

 agonal, rather thin-walled, uniform in regular rows. Medullary rays 

 not very prominent or resinous, I cell wide, distant 2-12 rows of 

 tracheids, more rarely 32. Resin cells prominent, usually distant in 

 very narrow zones of occasional growth rings. 



Radial. Rays somewhat resinous throughout, devoid of tracheids. Ray 

 cells chiefly straight or somewhat contracted in the summer wood ; 

 the upper and lower walls medium, unequal, distinctly perforate with 

 broad and unequal pits ; the terminal walls thin, often curved, entire 

 or locally thickened ; the lateral walls with rather large, oval, nar- 

 rowly bordered pits, the broadly lenticular orifice becoming oblong 

 in the summer wood, 1-2, or in the marginal cells 4, per tracheid. 

 Bordered pits round, somewhat distant in i row, not very numerous. 



