1906] WEISS—BARK IN SASSAFRAS 439 
in cross section. This form is retained until the outer cortex has 
become disorganized, after which they appear like narrow bands (ig. 
5,m). In radial section the rays are from four to fourteen cells across 
(fig. 6, m). 
In most of the ray cells the walls are slightly thickened and pro- 
vided with numerous simple pits. They usually contain starch and 
sometimes ethereal oil as well. When the cells are cut off by cork 
the starch disappears, showing that it is completely utilized; the oil, 
on the other hand, persists. Some of the ray cells between the strands 
of primary sclerenchyma become strongly sclerotic, and in some cases 
cells of this character completely bridge the space from one strand 
to another (fig. 1). They can be easily distinguished from the scle- 
renchyma cells, even in cross section, by their larger size and distinct 
lamination. In longitudinal section they appear short and resemble 
the stone cells of the outer cortex. 
Primary bast. 
The primary sclerenchyma occurs in well-defined bundles, averag- 
ing about fifty fibers apiece (figs. 1, 8, sc,). Most of these bundles, 
in a radial direction, measure from three to eight cells across. In 
most of the fibers the wall is so strongly thickened that the cavity is 
reduced to a mere slit; in some cases, however, the thickening is less 
and this is especially likely to be true in the middle of a bundle. 
Apparently the deposition of ligno-cellulose upon the cell walls is not 
completed until the second vegetative period. 
The primary phloem lies just within the primary sclerenchyma, 
between the latter and the secondary sclerenchyma, and forms a band. 
from three to five cells across in a radial direction (fig. 1, ph,). The 
Sieve tubes are more or less completely separated from the scleren- 
chyma by a layer of phloem parenchyma. The cells of this layer 
tend to be rectangular in cross section, and their slightly thickened 
walls have numerous simple pits. The sieve plates separating the 
segments of the sieve tubes are nearly always somewhat oblique 3 
they are supplemented by numerous lateral sieve plates, especially 
in the radial walls of the tubes. All of the sieve plates in the primary 
phloem soon become covered by deposits of callus. The companion 
cells conform to the usual type. 
