OF DENISON UNIVERSITY. 
27 
tinue the inflorescence, as in species of Lactiica and Delphinium. 
Besides, at this time the rapid production of blossom and fruit seems to 
exhaust the vital powers of the plant. Hence, accessory buds are 
usually found in greatest abundance above the middle of herbaceous 
plants, but not at the very tips of the branches. 
With ligneous plants it is different. Each year’s growth may be 
said to repeat the life of the tree, and the twig takes the place of the 
entire herbaceous plant. The period of greatest vigor in an ash twig 
is not when the sap has begun to flow and the leaves have barely seen 
the sunshine, but when most of the leaves have opened out their blades 
and are in full operation. It is the time when the upper part of the 
twig is developing. In the ash, where the terminal bud is already 
produced in June, the leaves last formed subtend accessory buds, while 
those formed earlier usually subtend only the single axillary bud. In 
young, vigorous shoots of hickory and walnut, the axils first formed 
contain a single bud ; those towards the middle of the branch, two 
buds, one of them accessory ; the axils later formed, from three to four 
buds ; and in very vigorous branches the last formed axils may contain 
even five buds. Many trees which usually do not form accessory 
buds (Draxinus Americana) (i) produce large and well developed ones 
in all the upper axils, when the tree has been cut down and the strength 
of all the roots is turned to the support of a few fresh shoots growing 
out from the old stump. 
The term superposed hnds was introduced to explain the existing state 
of things in ligneous plants, where they were first studied. Here the 
buds are really placed one above the other along the internodes of the 
plant, and frequently by the lengthening of the internode during the 
earlier part of its growth, the buds may be considerably removed from 
one another and the uppermost bud may be about an inch above the 
lowest, as in the Juglandaceae. In such cases the earlier and hence 
upper buds, being separated while the twigs were growing most rapidly 
are further removed from each other, than the lower buds, which grew 
during the less vital period of the twig’s development.* 
In Aristolochia Sipho (8) this superposition is less evident, for here 
the buds are arranged at about the same height in the leaf axil, so that 
superposition exists only hypothetically. Although evidently super- 
separation of superposed buds, caused by the varying growth of the in- 
ternodes, was noted several years ago by Mr. W. B. Werthner, who first called 
my attention to it. A. F. F. 
