Boodle—Anatomy of the Hymenophyllaceae. 467 
seats the petiolar bundle of H. tunbridgense , and should be 
compared with the rhizome of the same species (Fig. 16). 
Another case of a sieve-tube in contact with a tracheide occurs 
in Fig. 17. Figs. 15 and 14 show the structure of the petiole 
and rhizome respectively of H. fucoides; the same difference 
is presented as in H. tunbridgense . In H. polyanthos and H. 
Smithii the petiolar bundle is collateral, with a xylem of the 
form found in the rhizome, while in H. javanicum and . other 
species it could not be determined whether the phloem was 
interrupted, the material not being well enough preserved. 
H. sericeum and H. ciliatum differed from the other plants of 
this series in not having typical collateral structure in their 
petioles. In H. sericeum the xylem is shaped like the letter 
Y, with protoxylem forming the ends of the two arms, and in 
H. ciliatum the xylem is very small, but has the form of 
a curved arch with the ends turned inward, and with proto¬ 
xylem at the two extremities ; in this species two or three 
scattered sieve-tubes occurred on the upper side. 
Hymenophyllum, nodal region. 
Axillary branches occur very generally in the Hymeno¬ 
phyllaceae 1 , at many nodes, however, the rudiment of the 
axillary branch may remain undeveloped. The stele of the 
axillary branch is inserted on the leaf-trace. Figs. 9-12 are 
drawings of transverse sections of the node of H. dilatatum , 
var. Forsterianum , which show the behaviour of the leaf-trace 
and axillary branch. In Fig. 9, Plate XXV, the stele of the 
rhizome (s) is seen on the right, cut transversely, and on the 
left the leaf-trace [l.t.) is fusing with the stele of the axillary 
branch, both of them being in oblique section. In Fig. 10 
the large stele on the right belongs to the rhizome, the small 
one on the left is the leaf-trace, i.e. the product of fusion 
of the leaf-trace and stele of the branch. The phloem of the 
leaf-trace (pk 1 ) may be recognized by the small size of its 
elements as compared with the pericyclic cells, and forms 
1 Prantl, 1 . c., p. 25. 
I i 2 
