1906] WEISS—BARK IN SASSAFRAS 437 
small concave depressions in the cuticle. The number of the hairs 
"varies, and in a general way is inversely proportional to the number 
of stomata. Thus, in a moist locality few hairs are formed, while 
in a dry region they are very abundant. In a meso- 
phytic area some trees bear few hairs, while others 
under the same conditions bear very many. It would 
appear from this that the production of hairs was 
primarily due to individual peculiarities of the tree in 
question and secondarily to the external conditions 
under which the tree developed. 
Outer cortex. 
The outer cortex comprises everything external to yc, 4-—Epi- 
the primary sclerenchyma except the epidermis. It is dermal hairs on 
composed of a ground mass of parenchyma with ia iis 
scattered stone-cells. No crystal cells occur. With ” 
the formation of cork the outer cortex gradually becomes disorgan- 
ized and eventually disappears. . 
In cross section the parenchyma cells vary from elliptical to rec- 
tangular in outline, the long diameter running in a tangential direction 
(jig. 1, p). They vary considerably in size and some of the larger 
cells have their walls slightly lignified. Most of the cells, however, 
have thin walls, which may or may not be provided with simple pits. 
Many of the smaller cells contain starch and this is especially likely 
to be true of those which border the strands of sclerenchyma. The 
presence of ethereal oil in the parenchyma can be demonstrated by 
appropriate tests, but it does not seem to be localized in special cells. 
In all probability the oil represents an excretory product of the proto- 
plasm of the parenchyma cells, and this fact would account for its 
general distribution. 
The stone cells form a continuous or interrupted layer extending 
entirely around the stem (fig. 1, st). They sometimes lie next to the 
epidermis and are sometimes separated from it by one or two layers of 
parenchyma cells. The stone cells are at first circular in cross section 
but afterwards become flattened and assume an elliptical outline. 
In radial section they appear rectangular, being about three times as 
long as broad. Their walls are strongly thickened by deposits of 
