174 BOTANICAL GAZETTE : [SEPTEMBER 
Fig. 7 shows the more prominent features of the anatomy of a 
young box elder root. The pith is almost all eliminated by growth 
pressure. Medullary rays are numerous, straight, 1-2-seriate, and 
expanded considerably in the inner bark. Tracheae are large 
and very numerous, often in clusters of 5 disposed in radial rows. 
Tracheids are large, and of thin-walled and thick-walled sorts dis- 
posed in irregular groups in such a way as to give a marbled appear- 
ance to the section. The cambial zone in growing roots is 8 or 
ro cells thick. The bark is comparatively thin, and contains but 
very few sclerotic, crystallogenous, or tanniniferous cells. The 
many large sap-storage cells and canals are a conspicuous feature 
of the bark. The dead bark scales off in small thin plates, leaving 
the root quite smooth, in striking contrast to the appearance of the 
older stems. 
A comparison of figs. 6 and 7 makes it evident that the maple 
root is heavily charged with tannin in the older part, the wood 
is more compact, the bark is thicker, more dense with numerous 
groups of stone cells, few sap reservoirs, and it scales off in larger 
plates. The cambial zone is not so extensive, and everything 
about the structure points to a less vigorous functional activity in 
the root of the maple than in the root of the box elder. The 
appearance of the medullary rays in the outer wood and bark of an 
older root of Acer rubrum is shown in figs. 11 and 12. Fig. 12 
also shows fairly well the irregular massing of the sclerotic cells of 
the bark. Assuming the root to be a very conservative structure, 
it is interesting to compare this figure with figs. 13-16 inclusive, 
which show corresponding regions in some stems. 
Reference may here again be made to the remarkable rhizo- 
genetic powers of box elder stems when covered with water or 
buried in moist soil. Young shoots may be propagated by cuttings 
or by ‘‘layering,” as in the case of many berry canes. 
Anatomy of the stem 
The young shoots of box elder are commonly of very robust 
growth, especially in the male plants, and on all second growths. 
Not infrequently the season’s growth may reach a length of 5 or 6 
feet, with a basal diameter of five-eighths of an inch or more. The 
