1915] PLOWMAN—BOX ELDER 173 
In the series of hothouse experiments already mentioned, it 
was observed that all lateral buds in the box elder are of nearly 
equal vitality, and that most of them spring into active development 
at the first favorable opportunity. It was also observed that the 
box elder twigs were able to develop a much greater amount of 
new growth from their stored food material than were true maple 
twigs or even poplar and willow twigs of the same size. In the 
matter of rhizogenetic capacity, the twigs of box elder compare 
well with those of black poplar, and while the development is not so 
rapid as in the case of willow twigs, the number of roots developed 
is considerably greater, one or more appearing at every lenticel. 
Thus the propagation of the box elder by cuttings is comparatively 
easy, while in the case of true maples it is well-nigh impossible. 
On the older trunk surfaces the bark of the box elder shows a 
very characteristic ‘expanded metal” appearance, with the rather 
blunt ridges arranged in a fairly regular oblique diamond pattern, 
as shown in fig. 2. This is wholly unlike most of the true maples, 
in which the bark is seldom ridged, but in which it usually scales 
off in larger or smaller thin plates, as shown in fig. 3. The most 
notable exception to this rule among maples is Acer platanoides, 
which, by the way, seems to be one of the few contact points between 
the true maples and the box elder. In fact, the trunk surface of 
the box elder is strikingly similar to that of the white ash, even 
to the gray or grayish brown color. 
Anatomy of the root 
The root system of the box elder is very wide-spreading in 
comparison with the size of the tree. Slender fibrous roots are 
developed in immense numbers, forming a close-meshed network 
to an unusual depth in the soil. Where a larger root is uncovered 
and exposed to the air and light, buds appear and rapidly develop 
into vigorous shoots, much as in the case of the adventitious buds 
that form so abundantly on roots of the common locust, when they 
are exposed or injured. This bud-forming activity of box elder 
roots is especially marked when the main trunk has been injured 
in any way. Thus great clumps of second-growth shoots are likely 
to spring up around the stumps of recently cut trees. 
