. 
830 THE AMERICAN NATURALIST. (Vor. XXXIX. 
Tangential— Rays very numerous, medium to rather broad, 2-seriate in 
part, resinous. Cells (1) uniform in the same ray but variable in different 
rays, oval or squarish, unequal. Cells (2) uniform and narrowly oblong, 
strongly unequal, often several times higher than broad. 
2. .S. hookeriana Burr. 
Transverse.— Growth rings very broad ; the limiting wood parenchyma 
composed of rather distant and resinous cells. Vessels rather numerous, 
single or somewhat 2- to 3-compounded, oval, very gradually diminishing in 
size to the outer limits of the growth ring where they are 1 to 1 the diameter 
of the first. Medullary rays numerous, slightly resinous, 1 cell wide, dis- 
tant upwards of 8 rows of cells. 
Radial— Rays rather sparingly resinous. Cells (1) more resinous ; the 
upper and lower walls thick and very unequally, often sparingly pitted ; the 
terminal walls rather strongly though finely pitted. Cells (2) less resinous, 
the upper and lower walls rather thin and devoid of pits; the terminal 
walls strongly and finely pitted; the pits on the lateral walls minute, simple 
and often slitlike when opposite wood cells, but forming a coarse sieve- 
plate structure opposite vessels. 
Tangential— Rays numerous, resinous, sometimes 2-seriate in part, low 
to high, narrow. Cells (1) rather uniform and oval, chiefly equal. Cells (2) 
variable, narrowly oblong and more or less conspicuously unequal, rather 
thin-walled. 
3. S. uva-ursi Pursh. 
Transverse. — Growth rings narrow, variable, eccentric; the limiting 
wood parenchyma rather resinous and prominent; the wood cells thin- 
walled and squarish throughout with no obvious distinction of spring and 
summer wood. Vessels not predominant, 1- to 4-compounded and conspic- 
uously few toward the outer face of the growth ring. Medullary rays 1 cell 
wide, very sparingly resinous, not prominent, distant upwards of 6 rows of 
wood cells. 
Radial. — Medullary rays sparingly resinous. Cells (1), the upper and 
lower walls usually thin and not obviously pitted ; the terminal walls some- 
what strongly pitted. Cells (2), the upper and lower walls thin and not 
obviously pitted; the terminal walls finely pitted ; the pits on the lateral 
walls forming a strong sieve-plate structure ; Strongly predominant. 
Ti angential. — Medullary rays low to medium, very narrow, sparingly 
resinous, 2-seriate in part, the cells chiefly thin-walled throughout. Cells (1) 
uniform, oblong, to narrowly oval; equal. Cells (2) uniform, narrowly oblong, 
unequal, and often several times higher than broad ; usually predominant 
and often excluding (1). 
