No. 467] STUDY OF THE SALICACEE. Ss 
rarely 3-compounded, especially at the outer limits of the growth ring where 
they are diminished to 1 size. Resinous wood parenchyma more or less 
prominent throughout the growth ring in association with the vessels. 
Medullary rays numerous, rather prominent and resinous, 1 cell wide, dis- 
tant upwards of 10 rows of wood cells. 
Radial.— Rays somewhat resinous. Cells (1), the upper and lower and 
terminal walls strongly though rather finely pitted throughout, more resin- 
ous than the next. Cells (2) less resinous, often predominant ; the upper 
and lower walls rather thin and sparingly pitted; the terminal walls strongly 
though finely pitted; the pits on the lateral walls variable, hexagonal, and 
forming a coarse, sieve-plate structure which more commonly becomes an 
open scalariform structure through transitional forms. 
Tangential.— Rays sparingly resinous, low to medium, numerous, nar- 
row. Cells (1) chiefly uniform, narrow, oblong, equal. Cells (2) uniform, 
narrowly oblong, very unequal and often several times higher than broad, 
less resinous than (1). 
14. S. amygdaloides Anderss. 
Transverse.— Growth rings broad; the limiting zone of wood paren- 
chyma 1 to 4 cells thick and not obviously resinous. Vessels broad, oval, 
at first predominant, soon diminishing slightly in size and number toward 
the outer face of the growth ring where they are again somewhat abruptly 
reduced in size; at first oval, rather broad, and 1- to 4-compounded ; finally 
much reduced in size and width and becoming 4- to 5-compounded. 
Medullary rays numerous, 1 cell wide, not resinous, and distant upwards of 
16 rows of wood cells. 
Radial.— Medullary rays more or less resinous. Cells (1), the upper, 
lower, and terminal walls rather thin and finely, the first obscurely if at all 
pitted. Cells (2), the upper and lower and terminal walls rather thin, | 
last finely but conspicuously pitted ; the pits on the lateral walls forming 
a coarse sieve-plate structure often coalescing to form an open scalariform 
structure. 
Tangential.— Rays very numerous, resinous, medium, chiefly narrow, 
I-seriate. Cells (1) somewhat variable, oval or chiefly oblong and narrow, 
more or less conspicuously unequal. Cells (2) chiefly uniform, unequal, 
often several times higher. 
15. S. discolor Muhl. 
imiting zone of wood paren- 
throughout, radially oval, and 
ly at the outer limits of the 
rays resinous, 
Transverse.— Growth rings broad, the | 
chyma chiefly resinous. Vessels predominant 
2- to 4-, more rarely 5-compounded especial 
growth ring, where they are diminished to } size. Medullary 
