42 
Scott. — On a Palaeozoic Fern , the 
of the leaf. They are quite distinct from the foliage-leaves and much more 
numerous. The small trace supplying each aphlebia traverses the cortex 
with a steeply ascending course. These bundles, unlike those of the true 
leaves, have no effect on the general morphology of the stele. On entering 
the aphlebia the vascular strand undergoes one or more divisions. In calling 
the scales £ aphlebiae ’ it is implied that they are of the same nature as the 
outgrowths borne higher up on the rachis of allied leaves. As Paul 
Bertrand has stated (’ 09 , p. 109), their vascular strands in Z. Grayi and 
Z. scandens are given off from the leaf-traces ‘ avant meme leur individualisa- 
tion complete’. 
Lastly, there are the adventitious roots ; they are much less numerous 
than the aphlebiae and their steles pass out almost horizontally through the 
cortex, a fact which enables them to be easily distinguished. The roots, so 
far as observed, are diarch ; the roof-stele is inserted laterally on an arm 
of the main stele near its extremity (see PL V, Fig. 14). 
The above description would apply almost word for word to the 
Zygopteris scandens of Stenzel as well as to Williamson’s species. William- 
son, indeed, when he first saw Stenzel’s paper of 1889, was inclined to 
assume that the two species were identical (Williamson, ’ 89 , p. 157). We 
shall find that the new specimen from Shore presents some slight differences 
from the described specimens of both species. 
The old genus Zygopteris of Corda, characterized by the H or double 
anchor form of the foliar bundle, has been broken up in Dr. P. Bertrand’s 
memoirs, and among the smaller genera created out of it are Ankyropteris 
(founded as a subgenus by Stenzel but redefined by P. Bertrand) and 
Etapteris (P. Bertrand, ’ 09 , pp. 206, 218). The distinction is based on the 
petiolar structure ; the well-known species Z. (. Ankyropteris ) bibractensis and 
Z. (. Etapteris ) Lacattii may serve as types of each. Among the most 
important diagnostic characters of the two genera are : 
Ankyropteris. Ramifications of the frond in two series, one on each 
side of the rachis. 
Etapteris . Ramifications of the frond in four series, two on each side. 
Ankyropteris. Peripheral loops of small-celled xylem permanently 
present on the flanks of the foliar bundle. 
Etapteris . Peripheral loops absent. 1 
Ankyropteris. Adaxial longer than abaxial antennae. Middle band of 
bundle often curved, with concavity outwards. 
Etapteris. Adaxial and abaxial antennae of equal length. Middle 
band of bundle straight. 
The question whether Zygopteris Grayi belongs to Ankyropteris or 
Etapteris is disputed. Dr. P. Bertrand takes the former view and suggests 
that the petiole may possibly be identical with Ankyropteris bibractensis , 
1 Except perhaps temporarily in E. tubicaulis (P. Bertrand, ’09, p. 206). 
