Section IV., 1911. [43] Trans. R. S. C. 
The Origin and Development of Resin Canals in the Coniferw, With 
Special Reference to the Development of Thyloses and their Correla- 
tion with the Thylosal Strands of the Pteridophytes.* 
By Simon Kirscx, M.A., Ph.D., Former Demonstrator in Botany, 
McGill University; Expert, Forest Service, U. S. 
Department of Agriculture. 
Presented by Prof. A. G. NicHouts, M.D., and read May 17, 1911. 
In a recent publication (15), the author of the following memoir 
dealt with the origin and function of certain canals which occur in the 
vascular bundles of the Pteridophyta, and the subsequent blocking up 
of these passages by thylosal outgrowths. 
The critical study of the resin passages of the Coniferæ was sug- 
gested by Prof. D. P. Penhallow as a subject presenting many apparent 
points of similarity, especially in regard to the appearance of thyloses, 
and resulted in the investigations detailed in the following pages. At 
the very outset, however, it may be stated that, although the phenom- 
enon of thyloses was observed to exhibit the same characters and 
to follow the same general rules as in the Pteridophyta, the canals were 
found to be structures of an entirely different order, not only as regards 
their function, but also with reference to their mode of development. 
Thus while the canals of the Pteridophyta are always found in the 
vicinity of the protoxylem and owe their origin to the presence and 
the particular character of the protoxylem elements, the canals in the 
Coniferæ are capable of appearing at any point in the vascular cylinder, 
their presence and position depending entirely on the general conditions 
of growth and activity of the plants in which they occur. Moreover, 
whilst the canals in the Pteridophyta, in the majority of cases at least, 
arise by a combination of schizogenetic and lysigenetic activity, those 
in the Coniferæ owe their existence to purely schizogenetic conditions, 
although in exceptional cases the breaking down of some cells may 
combine several canals into one. In this event, however, the lysigenous 
appearance is of a purely secondary nature, and is not comparable with 
that encountered in the Pteridophyta. 
Now, since there are, in reality, two distinct phenomena to be 
discussed, a division of the paper into two sections commends itself 
as tending to a greater clearness of exposition, and so the development 
of the resin canals will be dealt with first, leaving the character and 
significance of the thylosal growths to a later treatment. 
*Contribution from the McGill Botanical Laboratory. 
