[KIRSCH] ORIGIN AND DEVELOPMENT OF RESIN CANALS 71 
genous cavity-formation. This aggregation would be a distinct step in 
development since it is the result of a greater differentiation of tissues. 
The absence of the ducts in the later structures would probably be due 
to the slower growth of the vascular cylinder, and the withdrawal of 
food from these rings by the large cones. 
The appearance of the resin canals in the axis of the female cone is 
easily explained by following the same line of reasoning as above, for 
there is a very large amount of food available to the growing tissues 
and this would necessitate an increase in the conducting cells. The 
radial partitions which Jeffrey mentions as dividing some of the ducts 
(13, 444) are simply additional signs of rapid and vigorous growth. This 
point is well illustrated from a drawing of our own material. Fig. 27 
is from a section of Pinus strobus cut from a shoot exhibiting very active 
growth, and shows a very large aggregation of parenchyma cells in 
contact with several medullary rays. In this mass three cavities are 
seen which are separated by two cells. The tensions during the growth 
of this shoot were very marked, and so instead of only one intercellular 
space being formed, three originated in this mass. These spaces are, 
however, separated by very thin partitions, which, in some cases, would 
be ruptured and lead to the formation of very large ducts such as were 
frequently encountered in the material from which the figure was ob- 
tained. These would, therefore, attain their great size by lysigenous 
action. 
The seedling of Sequoia gigantea exhibits an interesting feature. 
Thus Jeffrey (13, 446) states that, “The resin cells which are so con- 
spicuous in the wood of the adult stem are much less strikingly present 
in the seedling, and the resin ducts are entirely absent even from the 
first annual ring.” Now the amount of food available at this period of 
the life of the plant is very much less than that available to vigorous 
branches of a mature tree and hence there is a corresponding reduction 
in the number of “‘resin” cells present. On comparing Figs. 3 and 17 
of Jeffrey’s paper (13) in regard to the first year’s growth of the vascular 
cylinder of the vigorous shoot and seedling, a great difference is seen 
both in the appearance of the pith and of the wood. In Fig. 3 of the 
branch the pith is seen to be very much ruptured by the vigorous growth 
at an early stage, just as was shown in our vigorously growing specimens 
of Pinus banksiana. The wood is composed of much larger lumened 
cells than in the seedling, and it can thus be seen that the presence or 
absence of the resin ducts is directly correlated with the vigor of growth. 
In his observations on the effects of wounds on the wood of Sequoia 
gigantea, the following very interesting passage occurs (13, 447): “It 
should be added, however, that the formation of parenchymatous wood 
containing a large number of resin cells and ordinary parenchyma cells 
