74 THE ROYAL SOCIETY OF CANADA 
wood parenchyma cells which are present to a greater or lesser extent, 
in all Conifer, and the aggregation of these cells is a step forward in the 
differentiation of structure. Moreover, the appearance of the canals 
and their development in the forms under discussion depend mainly upon 
the amount of food available to the tissues of the plant, and on certain 
mechanical conditions, and this phenomenon could, therefore, develop 
independently in the different groups of the Coniferæ. If it were merely 
a case of reversion there is no special reason why the ducts should not 
appear in the male cone or in the first annual ring of the seedling of the 
forms under discussion. According to our view as to the nature of 
these structures, however, there are very good reasons for their non- 
appearance in the last named parts of the tree. 
The seedlings, especially in the first year of their growth, exhibit 
comparatively little vigor of growth and hence there would not be 
any particular need for a large number of wood parenchyma cells either 
for conducting or for storing foodstuffs. The development of Pinus 
palustris (Miller) affords an excellent example of this slow growth (87, 
55). “During the first three or four years its energy of growth is mainly 
expended upon the development of its root system. . . . . . By the 
end of the first year the stem of the plantlet is rarely over three-fourths 
of an inch in length, the main root having attained a length of from 
eight to ten inches. Having reached the end of the second year, the 
taproot is found from 2 to 3 feet in length, the stem scarcely 14 inches 
long, with an increase of diameter hardly perceptible . . . As far as 
could be observed the growth proceeds equally slowly during the fifth 
and sixth years, the plant at the end of that period being from 5 to 74 
inches in length.” The writer has not been able to obtain a seedling 
of this species but it would be interesting to examine one with a view 
of determining the number and distribution of the resin passages in the 
first annual rings of the seedling and root, and to compare this with 
the number of resin passages in the first annual rings of several branches. 
Such a comparison might yield us some valuable information as to 
whether the appearance of the strands of vertical parenchyma is 
governed by the phenomenon of reversion or by the law of demand and 
supply. 
In a subsequent paper (14), Jeffrey presents the results of further 
investigations of traumatic phenomena. In speaking of the traumatic 
resin canals, he says, “They are apparently for the purpose of sterilizing 
the wound by pouring large quantities of resin over its surface.” This, 
however, can not be their primary function for any sterilization which 
could be of use to the tree must take place immediately on wounding, 
while the canals are not formed at this period, but only during a certain 
stage in the growth of the wood. Then again, in cases like Sequoia 
