On Internal Phloem in the Root and Stem 
of Dicotyledons. 
BY 
D. H. SCOTT, M.A., Ph.D., F.L.S, 
Assistant Professor of Biology ( Botany ) Royal College of Science , London, 
AND 
GEORGE BREBNER. 
With Plates XVIII, XIX, XX. 
ODERN botanical research, especially during the last 
IVX fifteen years, has sufficiently demonstrated the im- 
portance of that modification of the more ordinary type of 
dicotyledonous structure, which consists in the presence of 
phloem on the medullary as well as on the cortical side of the 
vascular bundles. The term bicollateral , now generally used 
to express this arrangement of the vascular tissues, was first 
introduced by De Bary 1 . 
The structure itself was discovered in Cucurbita by Th. 
Hartig 2 3 in 1854, and by von MohP in the Asclepiadeae and 
other plants in the following year. From that time onwards 
internal phloem has been observed in a constantly increasing 
number of natural orders. Owing chiefly to the investigations 
1 Comp. Anatomy of Phanerogams and Ferns; Eng. ed. p. 338. 
2 Botanische Zeitung, 1854, P- 5 1 - 
3 Bot. Zeitung, 1855, p. 890. 
[Annals of Botany, Vol. V. No. XIX. August 1891.] 
