1897] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 333 
can be detached (jigs. r2 and 173, ¢). Cross sections of one of 
these vesicles shows an inner thin walled layer of cells (jig. 73, 
s), surrounded by 4 to 10 layers of strengthing cells, which are 
elongated or stretched in the peripheral direction (fig. 73, @). 
Secondary cortex (inner bark\.—The medullary rays of the 
secondary cortex are composed of starch and protein conducting 
cells. The protein conducting cells are best seen in radial sec- 
tions, where they form one layer on each side of the medullary 
ray. They are analogous to the protein conducting bast paren- 
chyma of many conifers. The starch conducting cells occupy 
the central part of the ray. 
The bast parenchyma cells are placed end to end in single 
isolated rows. Their cells are about 2 to 3 times as long as wide. 
The greater number are secretion reservoirs for tannin and cal- 
cium oxalate. Usually only one peripheral row of bast paren- 
chyma cells is formed each year. 
Bast fibers are absent in species of Abies and in the Abietinex 
Many of the bast parenchyma cells become thickened and scleren- 
chymatic. Like the sclerenchyma cells of the primary cortex 
they often branch. They are usually found in groups or nests 
extending the whole length of the internode. 
The remaining and by far the greater portion of the sec- 
ondary cortex is made up of the sieve tubes. They are arranged 
in radial rows and, as in all conifers, have their sieve plates on 
their lateral walls. No vertical or horizontal resin canals are 
present. B 
Wood. — The medullary rays are composed of starch con- 
ducting or normal pith cells only. The protein conducting 
Cells present in the rays of the secondary cortex are wanting. 
As in all conifers, the tracheids of the spring wood have larger 
lumina than the tracheids of the fall wood. No resin canals are 
present in the normal wood. 
_ ~Pith.—The pith adjoining the pith septum on its under side 
differs from the internodal pith in that it is composed of a mass 
. ; of loose cells, which break away from the septum, so that in 
__ two-year old and older internodes a cavity is formed immedi- 
