1915] CHRYSLER—RAYS OF CEDRUS 301 
the fifth and sixth annual rings of a branch of C. libani. It will be 
noticed that on the upper side of the ray the first marginal cell is 
a tracheid, followed at once by parenchyma, and on the lower side 
a tracheid is followed by a shadowy cell or “ghost,” which still 
shows a faint bordered pit, and is in turn followed by a row of 
parenchyma cells. It must be admitted that in some cases the first 
cells to appear on the margin of a ray are parenchyma cells, but 
the figure shows the prevailing condition. As far as such obser- 
vations afford evidence, they indicate that marginal tracheids 
antedate marginal parenchyma, and where only parenchyma is 
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Fic. 4.—C. libani, root; a crystal-bearing cell takes the place of starch-bearing 
parenchyma at the limit of growth ring; X 290. 
present it may be inferred that the earlier stages have been passed 
over. 
In a number of cases it has been observed that marginal paren- 
chyma cells are closely associated with resin cells. It will be 
recalled that in the genus Cedrus the resin cells occur on the outer 
face of the summer wood, and that it is at the limit of an annual 
ring that marginal parenchyma is most frequent. Fig. 7 shows 
the close relation of a row of resin cells to parenchyma cells of a ray 
in a branch of C. aélantica. It will be observed that the resin cell 
in view does not pass behind the ray, but that its end abuts against 
a marginal parenchyma cell which lies at the outer edge of a layer 
of summer wood, giving the appearance of a row of resin cells 
