No. 467.] STUDY OF THE SALICACEE. 833 
what thicker and very finely pitted ; the pits on the lateral walls forming a 
coarse, sieve-plate structure. 
Tangential.— Rays numerous, narrow, low to rather high, somewhat res- 
inous. Cells (1) uniform, oblong, chiefly equal. Cells (2) uniform, narrowly 
oblong, very unequal, and often several times higher than broad. 
9. S. scouleriana Bebb. 
Transverse.— Growth rings medium ; the limiting zone of wood paren- 
chyma somewhat resinous, 1 to 3 cells thick. Vessels somewhat uniform in 
size and number throughout, except at the outer limits of the growth ring 
where they abruptly diminish in size ; oval, rather broad, chiefly 1-, but fre- 
quently 2- to 3- more rarely 4-compounded. .Medullary rays numerous, prom- 
inent, resinous, 1 cell wide, and distant upwards of 8 rows of cells. 
Radial.— Medullary rays resinous. Cells (1), the upper and lower and ter- 
minal walls thick and strongly pitted throughout. Cells (2), the upper and 
lower and terminal walls rather thick and strongly pitted; the pits on the 
lateral walls forming a prominent sieve-plate structure. 
Tangential— Rays numerous, resinous, medium, narrow, I-seriate. Cells 
(1) narrow, chiefly uniform, oval or more generally oblong, equal. Cells (2) 
uniform, narrowly oblong but very unequal, and often several times higher. 
10. S. longifolia Muhl. 
Transverse— Growth rings usually very broad but very variable and 
sometimes very narrow. Wood parenchyma cells numerous, very resinous, 
and associated with the vessels as well as forming an open zone on the 
outer face of the growth ring. Vessels predominant throughout, especially 
in the earlier portions of the growth ring; at first rather large, oval, and 
1- to 3-compounded, later somewhat reduced, round, and simple or some- 
what 2-compounded. Medullary rays numerous, resinous, 1 to 2 cells 
wide, distant upwards of 6, or more rarely 10 rows of wood cells. 
Radial.— Medullary rays resinous. Cells (1), the upper and lower walls 
sparingly pitted, the terminal walls strongly but finely pitted. Cells (2), 
the upper and lower walls rather thick but not obviously pitted, the termi- 
nal walls very strongly pitted ; the pits on the lateral walls forming a coarse 
sieve-plate structure. 
Tangential. — Rays very numerous, resinous, 2-serlate in part. Cells 
(1) very variable, from narrowly to broadly oval, or round, or even — 
ish, very unequal. Cells (2) uniform, narrowly oblong but unequal an 
generally with thinner walls. 
| 11. S. cordata Muhl. 
Transverse — Growth rings broad, terminated by 2 to 3 rows of 2a 
flattened, rectangular wood cells ; the limiting wood parenchyma prominen 
