158 MISSOURI BOTANICAL GARDEN. 
wise increased in diameter. Two distinct flat surfaces are 
thus formed where the swellings above and below the band 
face one another. In the course of time, in certain cases, 
two years after the band has been on the twig, these two 
surfaces unite completely around the twig (pl. 22, fig. 2), 
and there is to all intents and purposes a union between 
the two swellings which resembles in many respects the 
union which takes place between two pieces of callous tissue 
after they meet from opposite sides of a wound. After 
the two surfaces have united, the development of the 
branch goes on as if there had been no girdling; and the 
band of the bag worm is enclosed within the swelling and 
may remain there for an indefinite period. Plate 22, fig. 
4 shows a branch of a maple tree ten years old. There 
are no signs visible on the outside, of any disturbance due 
to the insect except the old cocoon, which is still hanging 
from the lower side of the branch, with not only the slen- 
der filament, but also a large portion of the upper part of 
the cocoon enveloped by the wood of the maple. In the 
ease of the sycamore, maple and other rapidly growing 
trees the disturbance caused by the bag worm is generally 
only a temporary one, and in the many hundred cases 
found on these trees, there is not one instance where death 
followed the failure of a twig to break the band. 
The formation of the single swelling on the outside of 
the band is confined singularly enough almost wholly to 
the coniferous trees, in some of which it is extremely 
striking. The most remarkable cases of excessive swelling 
with subsequent death were found on a young tree of the 
Deodar cedar on the grounds of Tulane University, in New 
Orleans (pl. 24, fig. 5, 7, 8). A similar large swelling was 
found on a tree of Pinus virginiana growing near Wash- 
ington, D. C. (pl. 24, fig. 1). The only case of this kind 
among dicotyledonous trees was found in the locust 
(Robinia pseudacacia). Four trees of this species were 
found in a park in New York City with some ten swellings ; 
