206 BOTANICAL GAZETTE. [August, 
Structare and distribution of Resin Passages of the White Pine.* 
ETTA L. KNOWLES. 
WITH PLATE VII. 
First a study was made of the general structure of the stem 
and leaf of the white pine (Pinus Strobus) with reference to both 
the relation and structure of different parts. The Scotch pine 
was studied in the same way and afterwards a comparison made 
between the two. Stems of one and two years growth were taken 
of each species and put into alcohol for the purpose of removing 
’ resin, and the material thus preserved was ready for use as needed. 
aves of each and young shoots cut at intervals of a few days 
were treated in the same way. Thin sections were cut, stained 
with Schulze’s Solution and mounted in glycerine. For each 
point studied sections were taken of a dozen or more different 
stems. Drawings and measurements were all made with the 
camera. Upon comparing stems of the two species it was found 
that the general appearance is much the same, pith at the center 
and formed about it in successive rin 3, wood, cambium, phloem, 
cortex and epidermis, the main difference being that in the Scotch 
pine there is but one row of resin passages in the cortex and two 
rows in each year’s growth in the wood, while in the white pine 
there are two rows or rings in the cortex and one row in each 
year’s growth in the wood. In the cortex of the white pine the 
number of resin passages was found in some instances to be as 
high as 47 in a stem of one year’s growth, while in the Scotch 
pine 9 or 10 seemed to be the limit. Figures 1, Scotch pine, and 
2, white pine, show the distribution and arrangement of the resin 
passages in the two species in stems of one year’s growth; figs. 
Scotch pine one ring is irregular in outline and lies j ithin th 
: just within the 
wood surrounding the pith, as seen in figs. land3. The average 
einen ga ne BV ETERS 
__ *Selected for publication f riginal ‘ a ous 
the University of Mich igan, 1885-86. a 
