62 THE ROYAL SOCIETY OF CANADA 
functions to perform; viz., the conduction and storage of the elaborated 
foodstuffs. 
That the number of medullary rays can be abnormally increased 
under certain conditions of growth has been shown in the case of Juni- 
perus communis and Abies balsamea, and, as far as observation goes 
holds good for the Conifers as a whole, for in this group the medullary 
ray system is normally very weakly developed as compared with that 
in the Dicotyledons. It is, therefore, evident that the amount of food 
available for the cambial elements in the first growth of the vascular 
bundle, or the amount brought to the cambium by the rays already 
present cn the first appearance of secondary growth in thickness of the 
vascular cylinder may have a profound effect on the number, height, 
and disposition of the parenchymatous elements as represented by 
the medullary ray and its derivatives. But, as has been mentioned 
before, the growth of the medullary ray cells in a radial direction is 
very limited, and hence, on occasions where a very large supply of food 
is presented to the growing ray cells, they may evince a more or less 
marked tendency to keep on growing in a vertical direction. This 
tendency would of course be subject to specific or generic characteristics, 
some forms requiring a great deal more stimulation to exhibit the same 
degree of response than other forms would. This elongation, however, 
once induced would be general in the same vertical direction, even 
though it would tend to be rather localized in a tangential zone, and 
would insure the origin of a continuous multiseriate strand or cylinder 
of cells running in a vertical direction as extensive as the conditions 
which called it forth. That these cell aggregates would then be torn 
apart to afford an intercellular passage, would depend altogether on 
the extension of the elements surrounding them, the formation of the 
cleft being of a purely passive character. 
If the above is true, it would be expected that the so-called resin 
canals are not present in equal numbers at levels of the plant presenting 
differences in the vigor of growth, and that at the points where 
they are last formed the lumen would not appear in its characteris- 
tic form. All recorded cases support this view. Thus Mayr (19, 215) 
says: “In a mature stem the canals are by no means continuous as is 
claimed by Miiller. Thus in a very vigorous one year old shoot of the 
larch which was one metre long, there were in the upper part, as seen 
in transverse section, only four canals, in the middle portion twenty- 
six and near the base fifty-six canals. The very vigorous shoot of a 
mature tree of Picea excelsa showed forty-two canals in the upper part 
and one hundred and five in the lower portion. Anderson also, in 
describing the resin canals present in the tumor of Anies balsamea (2, 
340) states the following: “The greatest number is found in the middle 
