724 Boodle . — Anatomy of the Gleicheniaceae. 
thus A nodal island consisting of parenchyma and a ring 
of sieve-tubes appears in the xylem, but contains no sclerotic 
tissue or endodermis ; the arch of xylem outside this with 
three protoxylems separates for the leaf-trace, while the 
phloem of the nodal island becomes continuous with the outer 
phloem of the stele, part of it then apparently passing out as 
the internal phloem of the leaf-trace, and part remaining to 
repair the gap in the phloem of the stele. Apart from the 
absence of sclerotic tissue and endodermis here, the structure 
is not very different from what was found in one of the nodes 
of G. dichotoma (the fourth node described). 
As a node of G. dicarpa showed some points of difference 
from Poirault’s description (’ 93 , p. 173 ), diagrams of the node 
of this species are given here. Figs. 20 and 21 show two 
stages, in which the xylem of the leaf-trace is preparing to 
separate. In Fig. 20 the phloem ( ph . *) has curved into the 
bay of the xylem. In Fig. 21 the phloem forms a wide loop 
in the xylem-arch, and a group of brown sclerotic tissue (sc.), 
surrounded by an endodermis, has appeared in the pericycle. 
In Fig. 22 the sclerotic group holds a transitory connexion 
with the sclerotic cortex, its endodermis becoming continuous 
with the outer endodermis 1 . The sclerotic group then becomes 
shut in as it was before, and the leaf-trace becomes nipped off 
from the stele in the usual way, so that in Fig. 23 one sees the 
leaf- trace separate, and with a sclerotic group (sc., which is 
bounded by an endodermis) in its central parenchyma (peri- 
cycle). The type of structure is identical with what is found 
in certain parts of the petiole of G. dichotoma. The group of 
sclerenchyma, however, is only continued for a short distance 
upwards in the base of the petiole, its elements becoming 
reduced in number till none are left, but surrounded to the 
last by an endodermis. Fig. 13 shows the group reduced to 
two fibres, which are separated by an endodermis from the 
surrounding, sclerotic elements of the pericycle. 
1 Neither the presence of the endodermis surrounding the sclerotic group 
nor the connexion of the latter with the cortex appears to have been observed 
by Poirault. 
