170 BOTANICAL GAZETTE [AUGUST 
of the conducting and fibrous cells is shared by the parenchyma, and 
that it is the actual hardness of the wall rather than its structure 
and pitting which is related to the character of the stored food. 
We shall later suggest a cause for this relation. 
Conditions in starch fibers are of interest here. These are 
fiber-like, starch-containing cells, and are frequently found in the 
maples, willows, certain legumes, and other trees. Unlike the 
parenchyma cells, which are definitely connected with the water 
supply either by their position next to a vessel or tracheid, or by 
being linked therewith by other parenchyma cells, these starch 
fibers usually occur in the midst of non-conducting tissue, being 
surrounded by fibers of the ordinary type. They possess very 
small, frequently rudimentary, pits and usually are thick-walled. 
No instance has been observed by the writer where any reserve food 
but starch occurs in such cells, and this starch usually stains much 
more deeply with iodine than that of the ordinary parenchyma, 
indicating that its water content is lower. The persistent character 
of the food reserve in these starch fibers is evidently related both to 
their isolation from channels of water conduction and to their 
thick and pitless walls. 
Discussion 
These two main facts which our anatomical survey brings out, 
(1) that during the winter starch is commonest in regions remote 
from centers of conduction (both in xylem and phloem), and in 
cells with thick, well lignified, and small-pitted walls, and (2) that 
fat is most abundant close to vessels or tracheids, in the phloem, 
and in cells with thin or unlignified walls and large pits, at once 
suggest that the character of the food reserve depends primarily upon 
the ease with which water or substances carried in water have access 
to the storage cells. Where access is slow and difficult, the reserve 
remains in its.summer condition as starch. Where access is easy, 
it is converted to a greater or less degree into other substances, 
with the consequent appearance of fat. 
In storage cells the walls of which are unlignified, as in the 
phloem and cortex of all species, and the rays and canal epithelium 
of Pinus, starch is quite absent in the winter and fat is very abun- 
