26x 
Affinities of Peranema and Diacalpe . 
curved edges of the leaf-trace in Loxsoma and Davallia . The adaxial 
strands of the leaf-trace in Peranema and Diacalpe each possess two proto- 
xylem groups in the hooked portion of the strand (Fig. 6). The facts 
in Onoclea have an interesting bearing on this point. Thus in Onoclea 
orientalis the leaf-trace bundles at their insertion on the leaf-gap are two 
separate strands with hooks at each end. They are inserted just at the 
base of the gap and symmetrically on its limbs (Fig. 4, v). At a point 
higher up in the petiole, however, and before the departure of the pinna- 
traces, this pair of bundles becomes joined together and forms a single 
curved trace with hooked ends, from which the supply to the pinnae is 
given off in extramarginal fashion. The same condition is found in Onoclea 
sensibilis} 
I find in my specimens of Lomaria Spicant (Fig. 4, iv) that three 
bundles enter the dictyostele at the base of the leaf-gap, one in a median 
position, the other two in adaxial positions. 2 The two adaxial bundles 
have hooked ends. The median one has a slightly curved plate of xylem, 
rather constricted in the centre and suggesting that it has been derived from 
the back of a triangular bundle of the type of Gleichenia dicarp a (Bower, 
‘ Land Flora ’, p. 563, Fig. 314) through a suppression on either side of the 
central part of the limbs of the horseshoe. 
Lastrea Oreopteris (Duval-Jouve, PI. I, Fig. 2), another dictyostelic 
type, has a couple of strap-shaped leaf-trace bundles, which are inserted on 
either side of the leaf-gap, almost midway up the gap. In this case also the 
two widen and ultimately fuse to form a single curved strand in the petiole 
below the first pair of pinnae. 
In Athyrium jilix-foemina (Fig. 4, vi), on the other hand, the leaf- 
trace supply goes off from the base of the gap as a single triangular strand 
which almost at once breaks up into two strap-shaped bundles, and these 
below the first pair of pinnae fuse again into a single curved strand (Duval- 
Jouve, PI. I, Fig. 1), a case recalling that of Plagiogyria semicordata (Bowqy, 
TO, p. 431), in which a single curved strand breaks up into three parts, 
to reunite below the first pair of pinnae into a single strand. 
These facts would seem to indicate that the broken leaf-trace has 
originated from a single horseshoe-shaped or curved strand by a suppres- 
1 In Annals of Botany, 1911, p. 177, Sinnott considers the Onoclean double leaf-trace as an 
advance on the £ ancestral triangular mesarch bundle ’ — e. g. of Gleichenia Speluncae — and the ap- 
proximation of the two bundles as a movement towards the ancestral type. But the two bundles do 
come together in the petiole before the pinnae go off, and so make his 1 ancestral character \ Still 
(p. 167) the base of the leaf-trace is ‘ the seat of ancestral characters ’ ; ‘ here we should expect to 
find indications of what was the primitive foliar bundle in the ferns ’ ; ‘ in this portion the effect of 
changing external conditions . . . must be felt last and least.’ And yet the base of the leaf-trace in 
Onoclea sensibilis really shows an advanced condition (according to Sinnott’s own hypothesis) on 
what appears higher up ! 
2 This corresponds in substance, though not in exact detail, with the statement of Luerssen in 
Rab., Krypt.-Flora, vol. iii, p. 114. 
T 
