4 
Marjorie Gordon. 
is not so broad in proportion to the size of the pit, as is that of 
either the ray tracheid or of the ordinary tracheid. The borders of 
the two latter also completely surround the pores. The pits on the 
horizontal and terminal walls of the medullary ray cells are cut 
across in the radial sections of the wood. The bordered (unilateral) 
character of the pitting on the ray tracheid as it appears in section 
where it touches a parenchyma cell finally distinguishes this element 
from the simple pitted parenchyma cells of the ray. The appearance 
of such pitting is indicated in most of the figures (see Fig. 1, etc.). 
Text-Figs. 1—6 x 225. 
In line with both marginal and interspersed ray tracheids 
parenchyma cells are sometimes found—similarly shaped, and also 
scattered, as are the ray tracheids. Fig. 4 shows an interspersed 
ray tracheid which has to the left a parenchyma cell. Farther to 
the left, beyond the figure, is a gap and then another ray tracheid. 
Immediately to the right of the ray tracheid figured is a also gap, 
after which there is another ray tracheid. Several series of inter¬ 
spersed ray tracheids were followed towards the cambium and 
invariably they disappeared and ultimately were not replaced by a 
row of parenchyma cells, but the two parenchymatous portions of 
the ray simply came closer together and “ pinched out ” the tracheary 
elements. Figure 6 shows a marginal ray tracheid, which has a 
