46 THE ROYAL SOCIETY OF CANADA 
a means of communication with the outside air, thus providing a channel 
for the aération of the plant and the necessary interchange of gases. 
Material. 
The material used in the present investigation was collected 
mainly in the summer of 1907, according to lines laid down by Prof. 
Penhallow, and came from Mount Royal Park, Montreal, and the 
pineries of northern Quebec on the Lievre river. It consisted mainly 
of one and two year old lateral shoots of Pinus strobus and Pinus 
banksiana and some terminal shoots of young, vigorous trees of the 
same species. Some of these were preserved in a 5 per cent. solution 
of formaline, whilst others were killed in Fleming’s solution and pre- 
served in an equal mixture of water, alcohol, and glycerine. The 
shoots were collected at stated periods from the time of budding to 
their full growth, and comprised both weak and vigorous examples. 
The specimens from northern Quebee exhibited particularly strong 
growth and furnished the most striking results. 
The material thus gathered was sectioned by means of the freezing 
microtome and stained in either hematoxylin or Bismark brown, and 
turned out to be highly satisfactory, exhibiting all the details clearly and 
normally, the nuclei in particular showing prominently. In regard to 
the resin canals, the material selected was especially favorable, the 
beginnings of the canals being shown in the first differentiation of the 
tissues after the appearance of the protoxylem elements; in a zone of 
later growth in the same growth ring; and in the wood of the second 
year; and in the case of one of the shoots which was examined, well 
developed canals were found even in the pith. Before proceeding with 
the detailed account of the various features which came under observa- 
tion in the different sections, it will be well to give a short account of 
some of the most typical specimens of Pinus strobus and Pinus bank- 
siana as seen in cross section. For this purpose two lots consisting of 
specimens of both species obtained in the same place and at the same 
time, one lot having been picked a week later than the other, will be 
selected for comparison. These were taken at a period of very active 
growth (June 21 and June 28, 1907), and afforded some of the most 
significant phases in the development of the structures under discus- 
sion. 
The first lot consisted of vigorous shoots of both species in the 
second year of their growth and of the first year shoots growing on them. 
Of the latter, the shoots of Pinus banksiana were from 6 cm. to 10 em. 
longer than those of Pinus strobus, but of about the same diameter. 
. In cross section a great difference in the state of development of the 
