Conducting Tissue-System in Bryophyta. 25 
This layer, barely differentiated from the inner cortex, we 
propose to separate as a rudimentary pericyele . It is not, 
however, continuous with, and clearly has a different origin 
from what we have called the pericyclic arcs of the rhizome. 
It is considerably interrupted by the incoming leaf-traces. 
Bastit calls the hydrom ‘ moelle,’ the hydrom-sheath ‘ peri- 
cycle interieur,’ and the leptom (as limited by us) ‘ pericyele 
exterieur.’ He does not recognize the existence of sieve-tube- 
like cells at all, but mentions the fact that the ‘pericyele 
interieur ’ has starchy contents. The three terminologies 
arranged in parallel columns may be of assistance to the 
reader. 
Haberlandt. 
Bastit. 
f Moelle interieure 
Central thick-walled 
Hadrom 
1 Moelle exterieure 
hydrom-cylinder. 
Peripheral thin-walled 
V 
hydrom-mantle. 
Leptom 
( Pericyele interieur 
Hydrom-sheath. 
( Pericyele exterieur 
Ecorce 
Leptom. 
j Rudimentary pericyele, 
( Cortex. 
Rinde 
Our Figs. 20 and 21 will enable the reader to distinguish 
the different tissue-systems. 
The constitution of the stele cannot be properly understood 
without reference to the leaf-traces, to which we now turn. 
The general features of the bundle of the leaf of Polytri- 
chaceae have been well described by Haberlandt in Atrichum 
undulatum (pp. 403-4) and by Bastit in P. juniperinum . 
The former describes the living cells of the bundle as ‘ Leit- 
parenchym,’ while the latter describes them as ‘cellules en 
forme de tibia/ We are able to confirm Bastit’s observation. 
In a transverse section of the leaf of P. commune , the living 
cells of the bundle form three rows parallel to the surface 
of the leaf. The cells of the middle row have the largest 
transverse section, are lined with a thin layer of protoplasm 
and contain no starch, while the top and bottom rows consist 
of slightly smaller cells (amylom) containing starch. At the 
corners of the cells between the rows are the two series of 
