522 Brebner . — On the Anatomy of 
type as haplomeristelic. In speaking of outgoing leaf-t races 
the prefixes mono , di , tri, &c. could be used, to simplify 
description. The use of meristele in the ways suggested 
is illustrated by a description of the behaviour of the 
outgoing leaf-traces in Danaea simplicifolia : e. g. in the 
very young seedlings the outgoing leaf-trace-meristeles are 
collateral, but the later- formed ones are concentric, just like 
the dictyomeristeles. The leaf-traces themselves are at first 
monomeristelic throughout their course, then dimeristelic 
through dichotomy, subsequently they are dimeristelic from 
the first, then they are trimeristelic, and finally in the most 
advanced seedlings examined they were found to be tetra- 
meristelic. 
The aim in suggesting, and adopting, the above modifica- 
tions in and additions to the stelar terminology was to get 
words which had as little as possible of theoretical connota- 
tion, and were at the same time fairly descriptive and clearly 
defined. Complete avoidance of theoretical connotation is 
of course impossible, nor is it always desirable. Time, which 
tests all things, will show if this attempt to simplify stelar 
terminology by increasing the number of terms was a wise one. 
Synopsis of Terms. 
Eustele. The ‘monostele’ of a typical Dicotyledonous 
plant. It consists of a ring of collateral or bicollateral meri- 
steles, and includes the pericyclic and medullary ground 
tissue. 
Actinostele. The ‘monostele’ of most roots and the simi- 
larly constructed stele of certain stems. It consists of alter- 
nating, or ‘ radially 5 arranged groups of xylem and phloem, 
surrounded by a pericycle. Pith may or may not be present. 
Atactostele. The monostele of typical Monocotyledons. 
It consists of a number of scattered vascular bundles imbedded 
in conjunctive ground-tissue. Also applied to the stele of 
Dicotyledons with meristeles not arranged in a single ring. 
In the latter, if the meristeles are all of one kind, described 
further as homodesmic , if of different kinds, as heterodesmic . 
