1913] CHRYSLER—PHLOEM OF ABIETINEAE 45 
of the root that the study was soon discontinued. THompson’s 
statement with respect to the ray tracheids may be aptly quoted in 
this connection (7, p. 108): ‘‘ The root is admittedly more conserva- 
tive than the stem. Accordingly in the latter the evolutionary 
processes are not so well represented. There is a hurrying over of 
the early stages, so that an actual series can rarely be observed.” _, 
Examination of the stem of a number of seedlings of P. Strobus 
and P. resinosa showed that (1) the rays in both the xylem and the 
phloem regions were without mar- 
ginal cells for several years; (2) B | | 
the marginal cells as a rule make ri 
their appearance slightly earlier in 
the phloem than in the xylem. 
This feature is shown clearly in 
roots as well; in fig. 11, from a 
5-year root of P. resinosa, is a 
triangular cambial cell which has 
cut off a succession of erect cells, 
while as yet no cells have been 
cut off on the xylem side. Fig. 7 
shows the same feature, and with Fic. 11.—P. resinosa, 7-year root: 
it may be compared the condition Fe perme pv atin ea 
represented in fig. 4. Addition of side but not on the xylem side; X 275. 
the marginal cells does not begin 
in all or many of the rays simultaneously, but after the plant is 
two to three years old a few of the rays acquire the border. 
With respect to the remaining genera of Abietineae, only a few 
species have been studied with any approach to thoroughness, but 
enough has been done to show that many of the features figured in 
this paper occur in Picea, Larix, Tsuga,and Abies. The same radial 
Sroups of cells occur, and the phenomena seen where two rays are 
vertically contiguous may sometimes be seen. For instance, fig. 6 
might be almost duplicated from a young root of Tsuga canadensis. 
The genus Abies presents points of interest, on account of the 
fact that most species lack marginal cells in the xylem, though they 
are generally present in the phloem. THoMPsoN points out that the 
frect cells are “never in line with the parenchyma cells of the ray, 



