MARATTIACEAE 529 
The shoot of the Marattiaceae, as a whole, being of a usual Fern-type, 
it will be considered in relation to the theory of the strobilus at the con- 
clusion of the Filicales. Meanwhile a comparison of the characters of the 
known representatives, modern and fossil, may be made, and this not 
only of the mature structure, but also of the details seen in the seedlings 
of the living forms. Such a comparison.-gives some foundation for an 
opinion as to the nature of the stock from which the family may have 
sprung. In the first place it had an upright, radially constructed shoot, as 
indicated by the fact that no dorsiventral fossil stem of this affinity has 
been described, while those which exist among the living genera are probably 
derivative: moreover the embryos are all upright, and radially constructed. 
Presumably it had a protostelic structure of the axis, as indicated by the 
simple anatomy of the young seedlings of the living genera. From this pro- 
tostele sprang the leaf-traces, at first without leaf-gaps, as is still seen in some 
living seedlings: the formation of leaf-gaps probably followed early as the stele 
dilated and became medullated. Each leaf-trace itself was a single strand, 
as is seen in the fossils even in the mature shoot, but only in the seedlings 
of the living genera: this would suggest some simple form of leaf in the 
ultimate parentage. The arrangement of the leaves was on a radial plan, 
but was probably simpler than in the living forms: this is indicated by the 
occurrence of early fossils with regular orthostichies of leaves. The root- 
system was endogenous, and after traversing the cortex with a more or 
less lengthy course, the roots emerged at the surface, forming sometimes 
a supporting external felt. The arrangement of the sori on the leaf was 
on the plan of a simple row on either side of the midrib, and the form of 
the sorus circular. The relation of the sporangia was probably synangial, 
and their number in each sorus small, or liable to be reduced to a solitary 
one. The individual sporangia were large, the spore-output numerous, and 
the mechanism of dehiscence simple, or altogether absent. 
These characters, which comparison would indicate as those of the 
Marattiaceous ancestry, show convergence in many points of form and 
structure towards the apparently distinct series of the Botryopterideae. As 
regards the reproductive organs also, it is to be remembered that certain 
Ferns referred to a nearer relation with the Botryopterideae have a more 
or less pronounced grouping of the sporangia into sori: this is suggested 
in Zygopterts itself (Fig. 272), and it is a marked feature in Corynepteris 
(Fig. 273). Thus the two families are not absolutely distinct even in this 
respect. It is probable that they represent divergent branches from some 
common primitive stock.? 
1 As regards relation to Pteridosperms, see Kidston, P27. Trans., 1906. 
21s 
