402 BOTANICAL GAZETTE [NOVEMBER 
Fig. 1 is from a section of the vascular bundle of the Cycas 
petiole cut so as to show the tangential walls of the tracheids of 
the primary wood. Spiral and scalariform elements of the xylem 
are shown at the left center of the figure, while the two transitional 
tracheids to the right of these exhibit the border-pitted condition 
typical of the region. Crossed pores can be seen in several of the 
pits, showing that the walls are not adjacent to parenchyma, but 
separate the lumina of two tracheids. The dark lines observable 
between the pits are thickenings in the primary wall and constitute 
the “bars of Sanio.” 
Fig. 3 is a portion of fig. 1 at a higher magnification and shows 
the part of the two border-pitted tracheids represented between 
(a) and (b) on that figure. The knife has passed diagonally 
through the wall of the left tracheid, leaving only a portion of one 
of the secondary layers, with parts of the primary attached to it in 
the upper region. In this area the bars of Sanio come out clearly, 
especially in connection with the fourth to the seventh pits from 
the top of the series. 
The forking which has been mentioned by JEFFREY as occurring 
in the bars which he found in the araucarian cone axis is indi- 
cated here. An extreme instance of this can be seen between the 
fifth and sixth pits from the top. These pits are farther apart 
than is usual, and the bar instead of having merely its ends 
forked is cleft throughout its length, half clinging to each pit, as 
a definite “rim” of Sanio. This seems to indicate a double 
origin for the bars, suggesting that each may have its origin 
in two “rims,” formed in the manner indicated by SANTO, 
one in connection with each pit. In the tracheid at the right, 
the bars are very plainly visible, though the forking is not so 
evident. 
The “rims” which form the bars in Cycas are characterized 
especially by two features. They invariably cling closely to the 
borders of the pits, and they are short, never reaching across the 
entire width of a tracheid, but only across that of a single pit. 
These are the two characteristics mentioned by THOMSON (8) as 
distinguishing the type of bar found in the Araucarineae from that 
in the members of the Abietineae. 
