714 Gwynne- Vaughan.— Observations on the 
Tansley and Lulham 1 , and the following observations confirm 
their account. The leaf-trace departs as a single strongly 
curved strand with the concavity, as usual, facing towards the 
median dorsiventral plane of the rhizome. The leaf-gap 
closes up at the same time as, or even slightly before, the leaf- 
trace is quite free. The sclerenchymatous ground-tissue lying 
in the concavity of the leaf-trace passes down with it into 
the substance of the stem-stele. In this manner it produces 
the leaf-gap itself, and also accounts for the stout strand of 
sclerenchyma, surrounded by endodermis and pericycle, that 
lies within the stele, near its dorsal side, in regions just below 
the nodes. If the strand of ground-tissue thus enclosed be 
followed downwards through the internode to the node below, 
it is seen to diminish gradually in size until finally it dis- 
appears altogether, usually a short distance before the leaf- 
gap next below is reached. So that in the lower part of each 
internode the whole space within the xylem is occupied by 
internal phloem alone (Fig. 21 ). Occasionally, however, the 
strand of ground-tissue may persist until that decurrent 
through the leaf-gap next below is also enclosed in the stele. 
In the specimens examined the ground-tissue decurrent through 
one leaf-gap was never found to be continuous with that 
decurrent through the gap below. Just before it disappears 
the enclosed strand sometimes breaks up into two or three 
small branches. 
The line of delimitation between the internal phloem and 
the xylem is not quite an even one, because small teeth of 
phloem project irregularly here and there between the peri- 
pheral elements of the xylem. The sieve-tubes of the internal 
phloem are unusually small and angular, and are scattered 
throughout the whole of its mass. They occur in greatest 
abundance towards the dorsal side, but no definite protophloem 
is to be distinguished. 
The stem branches frequently in a dichotomous manner. As 
the stele of the main axis approaches the point of branching 
1 On a new type of Fern stele and its probable phylogenetic relations. Annals 
of Botany, vol. xvi, no. lxi, p. 157, 1902. 
