64 THE ROYAL SOCIETY OF CANADA 
Russow (27, 139) states that ‘“ Wherever, e. g., in the Cupressineæ, 
wood parenchyma appears scattered among the tracheids, the pitting 
between these is exactly the same as between the tracheids and the 
cells of the medullary rays.”’ Strasburger, again, states that the rows 
of wood parenchyma are always connected with the living medullary 
ray cells by means of unbordered pits of the same character as connect 
the medullary ray cells themselves. 
Penhallow (25, 134), in discussing the resin passages of the genus 
Pinus, says: “In the outer epithelium the thin-walled elements may 
be associated with occasional thick-walled elements with which they 
are interchangeable, precisely as in the similar relations displayed by 
the medullary rays of Pinus pungens and Pinus cubensis. In the same 
region also there is a similar association with and transformation into 
parenchyma tracheids, which also has its parallel in the medullary 
rays.” 
It is thus rendered obvious that structurally the vertical aggregates 
of parenchyma are of the same nature, and display similar relations to 
the medullary rays in the regions where both are present. 
The same holds true as regards the cell contents of the two systems 
as far as recorded observation goes. Thus Mayr (19, 282) states: “It 
has been shown by Muller, Dippel and others, that the parenchyma cells 
of the wood, and as I can vouch, also those of the bast in as far as they 
are medullary ray cells, are resin forming cells. Thus in the woody 
cylinder all the parenchymatous cells of the medullary rays, some of 
the thickened (thick-walled) cells which act as epithelial cells, then the 
vertical parenchyma cells in the vicinity of the resin passage in particular 
the parenchymatous elements connecting two adjoining vertical pas- 
sages or a vertical passage with the adjacent medullary ray, all contain 
resinous matter.” As regards the starch contents the cells constituting 
the resin passage behave in an identical manner with those of the 
medullary rays, starch always appearing in the cells before resin is 
produced. 
Strasburger (833, 4) makes the following statement: “In the func- - 
tion of resin production, the medullary ray cells agree with those of the 
wood parenchyma, as in the heartwood of the Coniferæ they also show 
the presence of resin. Resin formation and the production of tannin- 
like substances are the last functions of the living cells of the medullary 
ray which precede their death.” 
The connections between the elements of the medullary ray and 
those of the vertical parenchyma aggregations are also of such a nature 
as to allow an uninterrupted flow of elaborated food from one living 
cell to another, whether these are placed in a vertical or in a horizontal 
direction. Strasburger (33, 20), in this respect, confirms the observa- 
