ON THE ANATOMY OF CHENOPODIUM ALBUM L. 
development of each individual zone of growth, the xylem of the bundle is 
formed first, its formation being followed by a change in the activity of 
the initial strand on the outer face of the cambium; from the active division 
of this strand the phloem is produced. There is little if any new xylem 
added to the vascular ring in those places where phloem initials originate, 
for the xylem of the bundles, as has already been shown, is developed before 
any of the phloem matures. The cambium then does not exhibit the uni- 
polarity which De Bary claimed for the group to which Chenopodium album 
belongs; it is always bipolar in restricted regions in that it gives rise to 
normal tissue elements on either side. . 
Summary 
1. The anomalous stem structure of Chenopodium album is produced 
by a periodically active cambium which forms xylem centripetally through- 
out its extent and phloem centrifu gaily in restricted regions. Where 
phloem is formed the cambium is "used up." The continuity of the cam- 
bium ring is maintained by the formation of new portions outside the 
phloem groups. 
2. The phloem of a secondary zone of growth is produced after all or 
most of the xylem has been formed. It is the normal product of the cam- 
bium and only belated in its development. 
3. The intermediary or conjunctive tissue is not ray tissue in the morpho- 
logical sense though it may function as such. 
4. The chief element of the phloem is the sieve tube with its companion 
cell. Phloem parenchyma is of only secondary importance. 
5. The stem structure shows in its ontogeny a striking similarity to 
the structure of the root of the sugar beet, a developmental study of which 
is contained in De Bary's " Comparative Anatomy." 
Laboratory of Plant Physiology, 
Cornell University. 
LITERATURE CITED 
1. Gheorghieff, S. Beitrag zur vergleichenden Anatomie der Chenopodiaceen. Bot. 
Centralbl. 30: 118; 31: 53-57- 1887. 
2. Sanio, C. Vergleichende Untersuchungen iiber die Anordnung der Elementarorgane 
des Holzkorpers. Bot. Zeit. 21: 389. 1863. 
3. De Bary, A. Comparative anatomy of the phanerogams and ferns, p. 594. 1877. 
4. Morot, L. Recherches sur les pericycles. Ann. Sci. Nat. VI. Bot. 20: 276. 1885. 
5. Fron, G. Racine et tige des Chenopodiacees. Ann. Sci. Nat. VIII. Bot. 9: 157. 1899. 
EXPLANATION OF PLATES 
Plate XVI 
A. Cross section of a large primary bundle showing arrangement of primary and 
secondary xylem; position and extent of phloem groups. 
B. Cross section of part of mature stem showing undulate appearance of the zones of 
growth; extent and position of the conjunctive tissue and the radial arrangement of the 
large vessels. 
