36 Bower.—Studies in the Phytogeny of the Filicales. VI 1 . 
Anatomy. 
The fundamental type of the vascular system in the adult axis in 
the genus Pteris is solenostelic, with an undivided leaf-trace. This is 
seen very typically in Pteris grandifolia , L., and it has already been 
noted also in Paesia scaberula (A. Rich). Kuhn, and P. viscosa , St. Hill. 
These may all be held as retaining a prevalent, primitive construction. 
But various modifications of this construction are found which may 
be held as derivative. The most common is the transition to dictyostely, 
resulting from the overlapping of the foliar gaps. This is noted by 
Gwynne-Vaughan 1 for Pteris tremida , R. Br., P. cretica , L., P.Jiabellata 
(? = P. semipinnata , Schkuhr), P. ( Anopteris ) heterophylla , Diels, and 
P. pellucida , Pr. To this list may now be added P. swartziana , Ag., and 
P. biaurita , L. In most of these the leaf-trace remains still undivided. 
But in some of them it comes away from the stele in the first instance 
as two separate straps. This is seen in P. cretica , L., and it matches 
very nearly, though on a much smaller scale, the condition seen in 
Lonchitis hirsuta , in Gymnogramme japonic a, and indeed in many other 
Ferns of more remote affinity. 
A more marked modification is that described at length by Gwynne- 
Vaughan, 2 viz. the appearance of accessory vascular strands. It is seen 
in Pteris elata , var. Karsteniana , Kze., now referred to P. ( Litobrochia ) 
Kunzeana , Ag., where the erect or oblique rhizome contains a perfect 
solenostele, with a more or less complete internal vascular cylinder; this 
is connected by a compensation-strand with the outer cylinder, which 
attaches itself to it at the anterior margin of each leaf-gap. The indi¬ 
cation how this polycyclic state may have arisen is given by comparison 
of the simpler condition seen in Dennstaedtia adia 7 itiodes 3 and rubiginosaP 
This is by no means the extreme example of polycycly in this affinity. 
Saccoloma elegans , Klf., has been described above. But this again is 
equalled or even exceeded by the complicated structure seen in the axis of 
Pteris (.Litobrochia ) podophylla , Sw. From material of this Fern collected 
in Jamaica it is possible to give a fairly complete account of the ontogeny of 
its very complicated stelar condition. 
The petiole of juvenile leaves of Pteris podophylla shows a simple leaf- 
trace which takes a horseshoe shape in those successively of larger size. In 
adult leaves it still remains undivided, but the lateral folds of the horseshoe 
become deeply incurved, as in Fig. 36, a. This is the condition seen at 
the base of the petiole. But in large leaves, as the upper region is reached, 
the lateral folds may meet and fuse, while below the lowest pair of pinnae the 
fused adaxial curves of the horseshoe may separate completely from the 
1 1. c., p. 697. 
3 1 . c., Fig. 2. 
2 1. c., p. 698. 
4 ]. c., Fig. 18. 
