1913] CHRYSLER—PHLOEM OF ABIETINEAE 37 
suggested by the fact that young rays altogether lack erect cells. 
This may readily be observed in a seedling or in the early layers of . 
growth of a stem or root. Attention has naturally been directed to 
the stage of growth at which the erect cells make their appearance, 
and a search has been made among the different organs of the plant 
for regions where a primitive condition would be likely to appear. 
The labors of Scott and of JEFFREY have shown that the 
reproductive axis is one of the places where primitive conditions 
frequently persist. It has already been shown (3) that ray tra- 
cheids are absent from the megasporangiate cone of Pinus; it may 
now be added that a search fails to reveal the presence of erect cells 
in the phloem region of the cone in Pinus, Picea, and Abies. 
Accordingly, the reproductive axis yields no results which apply 
to the present question. The leaf also is not well adapted to the 
present study, on account of the limited development of the 
phloem. The seedling, which has been studied with such advantage 
in other cases, has yielded results of much interest in the present 
instance, especially when the root is the part used. With the roots 
of seedlings have been compared young regions of roots of more 
mature plants. 
While Pinus has been made the basis of the present study, 
material of all the genera of Abietineae except Keteleeria has been 
available. Representatives of the hard and soft pines (P. resinosa 
_ and P. Strobus) and of species of Picea, Larix, Tsuga, and Abies are 
abundant around Orono, while material of Cedrus and Pseudolarix 
has been kindly supplied by Professor E. C. JEFFREY of Harvard 
University, and Pseudotsuga by Mr. F. D. Davis of Missoula, 
Montana. The pines of this vicinity have been supplemented by 
P. rigida collected by Mr. L. L. Woops of Wells, Maine, and 
P. cembroides, P. edulis, and P. aristata through the kindness of 
Dr. Forrest SHREVE of the Desert Laboratory, Tucson, Arizona. 
To each of these gentlemen I wish to express my obligation. In 
Providing material the difficulty has been to secure the necessary 
Stages; if the roots are too young the erect cells are absent, if too 
old the cells have collapsed to such an extent as to obscure their 
relationships. An age of about four to six years has been found to 
include the significant stages in P. Strobus, but older rootsmust be 
