Bower.—Studies in the Phytogeny of the Filicales. 509 
interest in this connexion. If the modifications there seen were extended 
into the solenosteles of the type of Dipteris, the state seen in the axis of 
Pl. alcicorne would be the result; or into the axis of the type of Matonia, 
something like what is seen in Pl. aethiopicum would appear. 
It has already been noted that in the young leaves of Platycerium the 
leaf-trace consists of only two strands. But in the mature state the trace 
comes off from the dictyostele of the axis as a number of distinct strands 
(PL alcicorne ), while in the more complex case where there is a medullary 
system in the axis, this also takes its share in the organization of the trace 
(PL aethiopicum ) [New Phyt., vol. xii, p. 317]. The constitution and further 
f 
Text-fig. io, i-xiii. Successive transverse sections of the petiole of Platycerium Hillii , 
showing the disposition of the vascular strands. After the stage shown in xiii, the midrib settles 
down to three strong strands disposed in the plane of the leaf-expansion, x 3. 
behaviour of the trace as it passes upwards into the leaf has been followed 
in the case of Pl. Hillii , a form nearly related to Pl. alcicorne. The actual 
leaf examined was one of the fertile type, as shown in Fig. 6 . Externally 
there is in the stalk an appearance as of a single central strand, or midrib, 
which throws off smaller veins right and left. But transverse sections show 
that the midrib is traversed not by one strand, but by a number of them, 
disposed in a circle (Text-fig. 10); and the condition is not unlike that 
seen in transverse sections of the leaf-stalk of Ophioglossum palmatum 
(Land Flora, p. 463, Fig. 259). 
Starting from the base of the petiole, the strands are seen at first to be 
disposed in a simple circle (Text-fig. 10, i) ; their number varies, owing to 
splittings and fusions, which extend even across the adaxial face of the 
