404 BOTANICAL GAZETTE [NOVEMBER 
to the width of a single pit. This is especially striking in the 
tracheid to the left, where opposition and even multiseriate pitting 
is in evidence. 
In fig. 5 is shown a section of the wood of the cone axis of Pinus 
resinosa near the primary xylem. It was difficult to get a good 
photograph on account of the irregularities in the tracheid walls. 
The figure illustrates the type of “rim’’ found in this region. The 
structures usually adhere closely to the pit borders, appearing as 
dark arcs, and not extending beyond the pits. One long bar, 
however, is shown just below the four pits at the top of the tracheid, 
passing across nearly the width of two pits, and thus presenting to 
some extent the appearance of the bar found in specialized abie- 
tinean wood. Such structures are exceptional. 
Fig. 6, from a radial section of the root of Pinus Strobus, shows 
a condition quite often found in the secondary wood close to the 
primary. Although the pits are large, the “rims’’ of Sanio, which 
are plainly in evidence, present the same characters as those of 
fig. 5. As one passes out from this region into the outer root wood, 
transitions are seen between this rim and the type shown in fig. 2. 
The rims become more and more separated from the pits. They 
also elongate and exhibit a tendency to fusion. The mature 
bar is thus often a complex structure and very specialized in char- 
acter. Similar transitions are seen in the cone axis in passing 
outward from the center. 
It is generally admitted that root and cone axis retain ancestral 
characters longer than the stem or branches, and the earliest formed 
parts of these are also accounted more primitive than the parts 
formed when the plant is older. If in this case the accepted reason- 
ing holds true, the Abietineae must have been derived from ances- 
tors which had bars of the araucarian or cycadean type. 
The discovery of “bars” or “rims” of Sanio in the primitive 
region of the cycads must either nullify their value as evidence of 
the derivation. of the araucarians from the Abietineae, or indicate 
that the Abietineae are also ancestral to the cycads, a position 
which can scarcely be assumed. Moreover, the study of the rims 
in different regions of the Abietineae indicates that the ancestral 
type of bar, as found in the cycads and araucarians, has become 
