306 BOTANICAL GAZETTE [May 
to be seen. This appearance is most readily interpreted as a per- 
sistence of marginal cells in the phloem after they have disappeared 
from the xylem. 
Summary 
1. The medullary rays of Cedrus are provided with a margin 
which varies greatly in composition, being made up of tracheids 
and parenchyma in varying proportion, or devoid of marginal cells 
for considerable stretches. 
2. Marginal parenchyma when present occurs at the limit of 
annual rings, and may also extend beyond this point so as to be 
more plentiful than ray tracheids. 
3. The constant occurrence of marginal parenchyma cells at 
the limit of annual rings, and their close connection with resin cells, 
indicates that parenchyma has replaced tracheids in connection 
with secretion of the so-called resin. 
4. The marginal cells in Cedrus show distinct evidence of being 
in a degenerating condition. 
5. The medullary ray structure confirms the view that Cedrus 
stands intermediate between Pinus and Abies. 
UNIVERSITY OF MAINE 
Orono, ME. 
LITERATURE CITED 
1. CHRYSLER, M. A., The origin of the erect cells in the phloem of the Abietin- 
eae. Bor. Gaz. 56:36-50. 1913. 
2. JerFrey, E. C. The comparative anatomy and phylogeny of the Conif- 
erales. Part 2. The Abietineae. Mem. Boston Soc. Nat. Hist. VI. 
131-37. pls. I-7. 1905. 
‘ , Traumatic ray tracheids in Cunninghamia sinensis. Ann. Botany 
22:593-602. pl. 31. 1908. 
4. PeNHALLOw, D. P., A manual of the North American’ Gymnosperms. 
Boston. 1907. 
5. STRASBURGER, E., Uber den Bau und die Verrichtungen der Leitungs- 
bahnen. Jena. r8or. 
6. , Lehrbuch der Botanik. Jena. 
7- THompson, W. P., The origin of ray tracheids in the Coniferae. Bot- 
GAZ. 50:101-116. 1910. 
, Ray tracheids in Abies. Bor. Gaz. 53:331-338. pls. 24, 25. 191 
8. 
