[KIRSCH] ORIGIN AND DEVELOPMENT OF RESIN CANALS 69 
for resin on the part of the tree calling forth the formation of ‘resin 
canals,’ is well illustrated by the following observations. 
Gomberg, in his article on the resinous contents of the longleaf 
pine (Pinus palustris, Miller) (35, 41), states that, “All the analyses, 
detail and average, show conclusively that the sapwood is compara- 
tively poor in turpentine; it is immaterial whether it comes from a rich 
tree or a poor one, from a tapped tree or an untapped one.” He also 
determined that the heartwood grows poorer in resinous substance as 
the pith of the tree is approached. This brings out the fact that the 
sapwood, where the recently formed resin canals are present, does not 
contain very much resin in comparison with the heartwood where the 
so-called canals would have lost their activity altogether. 
Fernow, in discussing the longleaf pine, records the following 
significant facts (86, 21): “The amount of resin in the wood varies 
greatly, and trees growing side by side differ within very wide limits. 
Sapwood contains but little resin (1 to 4 per cent.), even in those trees 
. in which the heartwood contains an abundance. In the heartwood the 
resin forms from 5 to 24 per cent. of the dry weight (of which about 
one-sixth is turpentine), and can be removed by bleeding, so that its 
quantity remains unaffected by the process.” This substantiates our 
view that resin formation is not a primary function of the so-called resin 
canals, because if it were, the greatest quantity of resin would be pro- 
duced when the tissues are most active. The large amount of resin 
present in the heartwood, however, proves that the resin is formed in 
the greatest quantities when the parenchymatous elements are nearing 
the end of their activities. Thus the low vitality of the medullary ray 
elements and of the wood parenchyma cells coincides with the produc- 
tion of a large amount of waste matter, which, in all probability, further 
reduces their vitality and helps to turn the living, active sapwood into 
the dead, mechanical heartwood. 
The appearance of resin canals under certain conditions of growth 
of an abnormal character, such as is brought on by wounding or disease, 
where these structures are normally absent, has received a considerable 
amount of attention from various writers. This phenomenon has 
usually been interpreted as an effort on the part of the plant to produce 
a substance which would sterilize the wound and prevent a rapid drying 
up of the exposed tissues. 
Jeffrey has treated this question fully, and reached certain conclu- 
sions, which, from a consideration of our results, seem to be of doubtful 
validity. Besides the traumatic phenomena, his conculsions also em- 
brace the non-traumatic occurrence of resin canals in certain parts 
of the tree such as the axis of the female cone and the first annual ring 
of very vigorous shoots, where they are normally absent in the wood 
