^4 New Fern-like Stem. 
95 
In regard to the last difference Count Solms remarks that 
M. Zeiller has figured for Psaronius brasiliensis and P. infarclus 
fusions of steles leading to a ring-like band (“ ringformige Schleife ”) 
or to a ring with but a small break. If we imagine this process to 
be extended to all the steles of Psaronius —a conception that Count 
Solms regards as offering no great difficulty—we should arrive at 
an image bearing a far-reaching similarity to the structure of our 
'Tietea. Specimens intermediate in this character between Tietea 
and typical Psaronieae do seem to exist, for Count Solms possesses 
an undescribed Psaronius from Brazil in which ring-like closed 
steles, or open branched ones such as are characteristic of Tietea , 
occur in many places. It is true that these steles occur only at 
the periphery, the central part being occupied by small crowded 
strands, of the type usual in Psaronius and strongly reminiscent of 
P. infarctus. If the comparison with Tietea were to be carried 
through we should have, Count Solms says, to assume the whole 
of the centre of the stem of Tietea to be missing, an assumption 
leading to an improbable, though not impossible, enlargement of 
the circumference of the stem. It is worth noting, however, that 
in Zeiller’s figures, as reproduced by Seward, 1 some of the more 
internal steles of P. infarctus itself are branched. Owing to the 
fragmentary preservation of the fossil Count Solms was unfortunately 
not in a position to study the traces, which would have shown 
whether the specimen was a Psaronius or a Tietea. It is to be 
regretted too that Count Solms’ photograph of this fossil (PI. VII, 
Fig. 7), rather less than life size, does not clearly show how far the 
polycycly of Psaronius was retained in this Tietea-Uke stem. 
While these facts afford some support for the view that the 
nearest affinities of Tietea may he with Psaronius —and this is all 
that Count Solms suggests—the marked polycycly of most of the 
latter seems to me a very serious difficulty. The origin of the 
polycyclic condition from the monocyclic has been so frequently 
traced of late years that it seems legitimate to conclude that it is 
always a derivative condition ; if so, Tietea may be derived from a 
more primitive monocyclic Psaronius. Dr. Scott mentions a 
Psaronius that, in part at least of its stem, seems to be not only 
monocyclic but monostelic. 2 This species seems, too, to have been 
solenostelic ; but this does not seem to me to make it any easier to 
see in it an anatomical resemblance to a precursor of Tietea. For 
though the evolution of so-called “ polystely ” from solenostely has 
been repeatedly traced and seems to be generally brought about by 
the overlapping of leaf-gaps, yet there seems to be no case known 
of the development in the ontogeny of several solenosteles from a 
single one, except in the case of such polycyclic solenostely as that 
of Matonia. Nor do I see how the numerous solenosteles of Tietea 
could arise from a single solenostele by any of the established 
tendencies leading to stelar complication. 
In the elaboration of its leaf-trace Tietea has followed a course 
to some extent parallel to that of the Marattiacese. Not only are 
the traces of both multifascicular from their origin, but in both the 
bundles are arranged in several series. In a large leaf of Angiopteris 
1 Seward, A. C. “ Fossil Plants. Vol. II.” Cambridge, 1910, p. 416, 
Fig. 296a. 
3 Scott, D. H. “ Studies in Fossil Botany.” Ed. 2, vol. I, 1908, pp. 301-2. 
