No. 467.] STUDY OF THE SALICACEE. 823 
L. P. fremonti Wats. 
Transverse-— Growth rings very broad, the limiting zone of wood 
parenchyma devoid of resin, I to 2 cells thick. Vessels large, broad, oval, 
becoming somewhat abruptly smaller toward the outer limits of the growth 
-ring ; I- to 3-, more rarely 5-compounded. Rays numerous, sparingly resin- 
ous, one cell wide, distant upwards of 12 rows of wood cells. 
Radial.— Ray cells (1), the upper and lower walls thin and finely pitted ; 
the terminal walls straight or curved and finely pitted. Cells (2), the upper 
and lower and terminal walls thin, very finely and obscurely pitted ; the 
pits on the lateral walls forming a coarse, sieve-plate structure. : 
Tangential— Rays medium to high, numerous, ı-seriate, very sparingly 
resinous, sometimes 2-seriate. The cells (1) somewhat variable, oblong and 
narrow or broader and oval, unequal. Cells (2) not conspicuously different 
but the terminal ones sometimes higher, the interspersed ones sometimes 
narrow. 
2. P. monilifera Ait. 
Transverse.— Growth rings medium to narrow, the limiting wood paren- 
chyma devoid of resin, in 2 to 3 rows. Vessels numerous throughout, 
broadly oval, becoming rather abruptly fewer at the outer limits of the ring, 
chiefly single, or less frequently 2- to 3-compounded. Medullary rays 
prominent, numerous, very sparingly resinous, and distant upwards of 6 
rows of wood cells, one cell wide. 
Radial— Rays sparingly resinous, the cells contracted at the entis. 
Cells (1), the upper and lower walls rather thick, unequal, and finely pitted ; 
the terminal walls thick, straight or curved, and finely pitted. Cells (2), the 
upper and lower walls thick and finely though remotely pitted ; the terminal 
walls often strongly curved, thick, and finely pitted; the pits on the lateral 
walls round, oval, or sparingly angled, in radial series. 
Tangential.— Medullary rays very numerous, low to high, very sparingly 
resinous, I-seriate or sometimes 2-seriate in part. Cells (1), uniform in the 
same ray and oblong, equal but in different rays ranging from very nar- 
rowly oblong to rather broadly oblong. Cells (2) not distinguishable. 
3. P. alba (Linn.). 
Transverse. — Growth rings narrow, uniform, the limiting wood paren 
chyma very sparingly if at all resinous, in I, sometimes 2 = gg 
rays prominent, somewhat resinous, I cell wide, distant upwards 0 r 
sometimes 10 rows of cells. Vessels broad, oval, or transversely A 
first predominant, gradually diminishing in size and number outwardly ; 1- 
to 2-, or more rarely 4-compo : 
