632 GENERAL COMPARISON OF THE FILICALES 
that that type was probably the tropho-sporophyll ; in fact, the Ferns show 
a Selago condition of their shoot. 
As in other Pteridophytes, so here the question is an interesting one 
at what period fertility of the plant may begin. In most Ferns the period 
is late, especially in the larger forms, and, as in the strobiloid types, this 
may be ascribed to a progressive sterilisation of the earlier leaves. But in 
other cases the formation of sori may happen relatively early, and these 
serve to direct attention to what was probably a more primitive condition. 
As examples where an early fertility is seen there may be quoted Blechnum 
lanceolata, Swartz, in which, however, no exact record was kept of the leaf 
on which sporangia were first seen. In specimens of Péris heterophylla, 
L. var. Zzternata, supplied by Messrs. Hill, the fourth or fifth leaf of the 
seedling already produced sori; but an extreme case is that quoted by 
Prantl,) of Lygodium subalatum, in which not only are the normal leaves 
fertile to the base, but it was noted also that the sub-primordial leaves, 
and even the primordial leaves bear ‘‘sorophores,” so that completely 
sterile leaves are hitherto quite unknown in this species. Such an example 
points clearly to the conclusion that in Ferns, as in other Pteridophytes, 
all the leaves of the sporophyte are potential sporophylls. 
A minor character too little used in comparison as yet is to be found 
in the superficial appendages. These may be filamentous or scale-like: 
the latter are readily recognised by their development as flattened expansions 
of the former. Speaking generally, the hair is characteristic of relatively 
primitive types, such as the Botryopterideae, Hymenophyllaceae, and 
Osmundaceae, while the scale or ramentum is found very generally among 
the Leptosporangiate Ferns, though it is also present in some of the Gradatae 
and Simplices. It is to be noted that in a considerable number of cases 
ramenta accompany a dictyostelic structure, though there is no constant 
coupling of the two characters. A good example of their phyletic signifi- 
cance is to be found in the Schizaeaceae, in all of which, excepting J/ohria, 
the appendages are of the primitive filamentous type; but in J/ohria, 
which is regarded on various other grounds as a relatively advanced genus, 
and has a dictyostelic stock, the appendages are flattened scales. It is 
possible that such characters may never acquire the systematic importance 
claimed for them by Kiihn,? but they certainly must not be overlooked as 
evidence having some degree of phyletic value. 
SPORE-PRODUCING MEMBERS. 
The sporangia of Ferns are usually grouped in sori; but apparent 
examples occur even among the most primitive types, as well as among | 
those which are more recent, of their non-soral disposition. The first 
question will therefore be, what was the mode of disposition of the 
sporangia in the first instance? 
| Schizaeaceen, p. 14. 2 Prantl, Zc., p. 13. 
