Conifers damaged by Squirrels. 341 
The piece of Thuya stem shown in the photograph is four feet 
high, the diameter of the wood at the base being lf-inches and at 
the apex about 1-inch. There are five islands of cortex and 
phloem separated completely from one another ; in some cases 
these islands encircle the stem, in others they are unilateral 
patches. The rings of bare wood separating these islands vary in 
in width, the lowest seen being about four inches, while the one 
above is seven inches wide. 
The three lower islands were all bearing living shoots when 
the specimens reached Kew, and in the case of the large island 
near the base these shoots were about four feet long and quite 
vigorous. 
The islands were consideraby enlarged towards the base, owing 
no doubt to the accumulation of metabolised products, as is the case 
in a tree which has been constricted with a tight band. Callus had 
been formed all round the injured surfaces and at the lower ends 
of the islands it was as much as an inch in thickness, in contrast 
to a thickness of only about aj-inch on the upper side. 
The Cupressus is in some ways a more striking example 
as the islands of the cortex are much more numerous and quite 
small. In every case a branch forms the nucleus of an island, and 
some of the islands are so small that callus has not been formed, 
and the branch has died shortly after the injury. Where larger 
islands have been left by the squirrels, callus formation, as in the 
Thuya, has taken place, and a conspicuous mass of swollen tissue 
has developed on the lower portion of these isolated pieces of 
cortex and bast. The apical portion of the Cupressus had died 
from the effects of the ringing, but the lower branches springing 
from the healed islands were growing vigorously. 
Both the Thuya and the Cupressus are of about the same 
age, and judging from the development of callus, the detached 
islands must have been in a living condition for two or more years. 
These cases are remarkable both as an example of the con¬ 
duction of water in wood unprotected by cortex and bark, and also 
of the continued conduction of water in old tracheids, since no new 
xylem can have been added to the now bare patches for at least 
two years. 
No doubt a considerable amount of water was lost in evapora¬ 
tion from the unprotected areas, and in the case of both the trees, 
the water supply does not appear to have been sufficient to reach to 
the summit. With regard to the descending current of metabolised 
