1904] JEFFREY—A FOSSIL SEQUOIA 325 
formation of traumatic resin canals. Where the irritation is most 
severe, 7. ¢., in the first annual ring formed after injury, there are 
apt to be both horizontal and vertical canals ; while in the later formed 
rings the impulse gradually dies out and only vertical canals originate. 
The horizontal canals run in considerable numbers from the margins 
of healing wounds. Fig. 3 represents a section through such a patch 
of traumatic horizontal canals. Fig. 8 shows the appearance of the 
large horizontal canal to be seen on the left of jig. 3 when somewhat 
more highly magnified. The enormously enlarged medullary ray 
is almost entirely taken up by the huge resin canal, which in turn is 
occluded by a mass of cells constituting a tylosis. Fig. 9 shows a 
smaller duct from the right of fig. 3 somewhat more highly magnified 
than the foregoing. The continuity between the tylosis and the wall 
of the duct can clearly be made out in this figure. The cells consti- 
tuting the walls of the traumatic resin canals in the Sequoias are 
thick-walled and much pitted, and generally contain in greater or 
less abundance the dark brown masses which occur in the resin cells 
of the wood of the Cupressineae in the larger sense. Not all of the 
canals contain tyloses in the fossilized material, but it is probable 
t they were universally present in the living tree. 
Fig. 10 shows the transition from a vertical to a horizontal duct 
#S seen in vertical radial section. The great difference in size which 
ordinarily obtains between the two sorts of ducts is very apparent. 
The abundant tyloses are also a feature of the horizontal ducts, 
although this phenomenon is also occasionally found in the vertical 
Tesin canals 
ol traumatic resin canals may extend very far above and 
om the Wound, so that in small isolated pieces of wood their relation 
From a wide knowledge of living forms of 
ty, I am in the position to state inductively 
oniferous w ts occurring vertically and tangentially in 
ods are always due to injury. It has been possible to 
that this is the case wherever the material was abundant enough 
ant a definite conclusion. 
onzontal traumatic canals ma 
 Tows of vertical] duc 
y pass outward from a healed 
Canals ¢ ough many annual rings. In one instance horizontal 
ned through thirty-eight rings of growth, ending in another 
