1911] HEMENWAY—PHLOEM OF JUGLANDACEAE 135 
consequently resemble those occurring in the resin canals of cer- 
tain conifers, rather than those found in the vessels of the angio- 
sperms. 
Summary 
The six species of the Juglandaceae which have been considered 
possess well developed lateral sieve plates which have the same 
structure and appearance and seem to function in the same manner 
as the sieve plates on the end walls. The callus on the lateral 
sieve plates is identical in character with that on the end walls. 
The large sieve tubes have lateral sieve plates which are as crowded 
and as large as the terminal ones. This is contrary to the accepted 
views in regard to the sieve tubes of the dicotyledons. It would 
seem that we have here to do with an ancestral character, which 
indicates that the lower dicotyledons, as exemplified in the Jug- 
landaceae, are more nearly related to the gymnosperms or vascular 
cryptogams. It is hoped that a further study of the phloem of 
the dictoyledons may disclose other ancestral traits, or aid some- 
what in a systematic classification from an anatomical standpoint. 
This work has been done in the Phanerogamic Laboratories of 
Harvard University under the direction of Professor E. C. JEFFREY, 
to whom the writer wishes to express his thanks for assistance and 
helpful advice. 
HARVARD UNIVERSITY 
EXPLANATION OF PLATE XIII 
Fic. 1.—Carya alba: radial longitudinal section of phloem. X 40. 
Fic. 2.—The same: tangential section of phloem. X40. 
Fic. 3.—A higher-power view of part of what is shown in fig. 2. X 180. 
Fic. 4.—Carya glabra: radial section stained to show callus on the sieve 
plates of the sieve tubes. X 180. 
Fic. 5.—The same: a similar view of the radial section. X 180. 
Fic. 6.—The same: showing a central portion of fig. 5 more highly mag- 
nified. X 500. 
