108 BOTANICAL GAZETTE [AUGUST 
“turning” along the ray and developing the buttresses characteristic 
of the ray tracheids of the hard pines. The lower part remains 
smooth. At this stage then, it is quite intermediate between a wood 
tracheid and a ray tracheid. . 
Farther from the cambium whole rows of tracheidal cells may be 
observed, each with a long tail-like projection extending from one 
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Fics. 9, 10.—Fig. 9, P. resinosa: young root; a row of ray tracheids with tail-like _ 
projections; fig. 10, P. Strobus: adult root; ray tracheids with “ tails.’ . 
end (fig. 9), and this end is always the one nearer the cambium. The 
“tail” is evidently the smooth part of the tracheid as seen at the 
cambium. Moreover, in Pinus resinosa the “tail” lacks the chat _ 
acteristic dentations present on the rest of the cell. Apparently then 
it is the result of an incomplete shortening of the tracheid. Fig. 1% 
from an old root of Pinus Strobus, shows that these projections persist 
in the mature wood, but, as is to be expected, they are neither 5° 
numerous nor so conspicuous. 
Stem 
The root is admittedly more conservative than the stem. Accord- 
ingly in the latter the evolutionary processes are not so well rept® 
