[KIRSCH] ORIGIN AND DEVELOPMENT OF RESIN CANALS ANR 
tissues, and hence the ray elements give rise to vertical aggregations 
of cells as soon as they appear in the cambial region, some of the primary 
rays giving rise to these parenchymatious proliferations even before 
any wood elements are formed or simultaneously with their formation. 
When the ray thus proliferating is of the multiseriate order, there would 
be the simplest connections between the lumina of the two cell aggre- 
gates on the appearance of the schizogenous cleft arising on the subse- 
quent extension of the woody tissues, and this feature is plainly shown 
in the figure. In addition, some of the ray elements which are not 
really parts of the vertical strand are also seen to have their major axis 
in a vertical direction. 
Mayr (19, 216) states that, “In a very powerful shoot, one centi- 
metre length of a vertical canal can give origin to seven horizontal 
canals, but on the average only four horizontal canals arise from this 
extent of a vertical one.” From what has been shown above, however, 
this is seen to be erroneous, as it is the more closely placed rays in a 
vigorous shoot which give this appearance. It is the rays which give 
rise to the vertical cells containing the intercellular passage and not 
vice versa. Moreover, not only do the multiseriate rays give off cells 
which form vertical passages, but the uniseriate rays behave in the 
same manner. 
Fig. 5 shows some of the medullary ray elements contributing 
directly to the formation of a vertical aggregate of cells containing a 
canal. The rays in this figure were uniseriate. A similar feature is 
represented in Fig. 26, which is drawn from a radial section of a second 
year shoot of Pinus banksiana. Some of the medullary ray elements 
in this case exhibit a vertical elongation in the protoxylem region 
and form part of a vertical aggregate of cells. 
It has been shown above that the so-called resin passages of the 
Conifer are not structures of a primary nature, such as the current 
view regards them, inasmuch as they do not arise from elements 
specially designated for them and which form a passage no matter 
where they occur. From what has been shown so far, it is tolerably 
clear that the vertical parenchyma strands are merely a portion of the 
medullary ray system, from which, in the forms under discussion, they 
are bound to occur under certain conditions of growth. Whether the 
elements forming these strands always arise directly from elements of 
the medullary rays, or whether they can, to a certain extent, arise 
independently in the cambial zone is a point of secondary importance. 
The point of primary importance that the author desires to bring out 
is that both the medullary ray elements and the vertical parenchyma 
elements owe their origin to the same causes, and have the same primary 
