166 Rhodora [SEPTEMBER 
summer wood being noticeably smaller than the rest and having slightly 
thicker walls. 'The radial walls of the tracheids are well provided with 
bordered pits, and half-bordered pits occur between ray-cells and 
tracheids. Pits on the tangential walls appear in only the last two 
or three rows of the summer wood. Resin-canals and resin-paren- 
chyma seem to be normally quite absent, though tracheids filled with 
resin or mucilage occur irregularly throughout the wood. 
A longitudinal radial section shows the tracheids crossed by medul- 
lary rays, which vary in height from two to twelve or more cells. 
"There are no marginal tracheids. ‘The ray-cells have very thin walls, 
and are often filled with “resin,” thus presenting a close resemblance 
to those of the modern Araucarineae (Fig. 2). The only pits observ- 
able are the half-bordered ones between the rays and adjacent trach- 
eids, there being none on the horizontal and terminal walls of the 
ra y-cells. There are from four to six lateral pits from a ray-cell to 
each tracheid with which it comes into contact. "These pits are circular 
in outline, and each has an oblique, slit-like mouth. "Тһе radial pits 
between tracheids show clearly in this section (Fig. 4). They are 
rather large and have elliptical openings, which are set obliquely, 
those on opposite sides of the same pit thus appearing to cross one 
another. No cases were observed in which a tracheid had more 
than one row of pits. In a few places the pits are flattened some- 
what by mutual contact, but in the great majority of instances they 
are circular in outline, though often occurring close together in long 
rows. А careful search was made for bars of Sanio between the pits, 
but in no instance were these discovered. "l'rabeculae were found in a 
few cases (Fig. 5), as were also septate tracheids. No wood-paren- 
chyma, however, was observable, though as above remarked resin- 
filled tracheids occur irregularly (Fig. 6). ‘The tangential pits on the 
face of the summer wood show clearly in this section. 
The longitudinal tangential section shows the rays to be composed 
of cells with oblong cross-section, resembling those of most of the 
modern Conifers (Fig. 3). The very thin walls of the ray-cells are 
evident. Where the section passes through an annual ring, the 
tangential pits appear in face view. They are smaller than those on 
the radial walls, and sometimes occur in more than one row to à 
tracheid. In such cases, however, there seems to be no regular ar- 
rangement of the pits. 
- The structure of the normal wood is therefore very simple. A num- 
