Bower.—On Medullation in the Pteridophyta. 563 
glossales, and Marattiales, that the axis of the embryo is vertical, and that 
it grows directly into the upright seedling. But in the Leptosporangiate 
Ferns the embryo is prone at first. Nevertheless the radial upright stock 
is established at once in many Ferns. In fact, in plants which are radial in 
the mature state the initial condition of the recumbent embryo does not 
impress dorsiventrality on the seedling. 1 This is the case for Osmnnda and 
Todea , so that for all practical purposes in the development of the stele 
these genera may be held to have had vertical axes from the start. It is 
uncertain what may have been the condition of other Leptosporangiate 
Ferns as regards their phyletic history, but it is significant that those great 
parent stocks, the Gleicheniaceae and Schizaeaceae, include prostrate forms 
among their most primitive types. This question will be discussed more 
fully on a later occasion. 
It has been seen that those Lycopodiales which are pithed were upright 
microphyllous forms, with intrastelar pith. The same may be said for the 
Equisetales, though here the formation of pith and degeneration of the 
primary wood has gone much further. 2 But the Ophioglossaceae and 
Marattiaceae, together with the Osmundaceae, are megaphyllous forms 
with upright stocks. The question will be, What is the nature of their 
medullation ? Of these the Marattiales, with their very complex dis¬ 
solution of the vascular system into separate strands, present a peculiarly 
complex problem of their own, and may for the present be left on one side. 3 
The most interesting cases of megaphylly with a vertical stock among 
forms which may be held as primitively upright are then the Osmundaceae 
and the Ophioglossaceae. 
The Osmundaceae are still the centre of keen discussion in respect of 
the source of their medullation. The one view is that the stelar condition 
seen in the living examples of the family is the result of reduction from 
a more complex condition, which was that of the ‘ amphiphloic siphono- 
stele This view is based on the study of the current representatives of 
1 1. c., p. 214. 
2 For the conclusions of a discussion of the stelar condition in the Equisetales, see Land Flora, 
p. 391. I see no reason to change the opinions there expressed, though the subject has been again 
opened by Eames (Ann. of Bot., 1909, p. 587). 
3 It may be noted that Farmer and Hill (Ann. of Bot., xvi, PL XVI, Figs, n-13) have illus¬ 
trated the origin of a pith, which can only be intrastelar, in Angiopteris. Brebner (Ann. of Bot., xvi, 
p. 550) points out that Danaea differs from Angiopteris and Marattia in not passing through a medul- 
Jated stage. Further, since this paper was drafted, Miss Charles’s paper ‘ On the Anatomy of the 
Sporeling of Marattia alata ’ has appeared (Bot. Gaz., Feb., 1911, p. 81). A comparison of her 
Fig. 8, PI. IX, with my Fig. 8 for Botrychium Lunaria shows a substantial similarity. In both 
cases there is intraxylic parenchyma, and apparent intrusion of parenchyma lying more externally. 
But after this the parallel seems to cease, and Marattia takes its own divergent way. Thus the 
evidence, so far as it goes, indicates that in the Marattiaceae a pith may be absent altogether : or it 
may appear temporarily before the peculiar break-up of the stelar system into meristeles. But in any 
case it is partly, or perhaps even wholly, intrastelar, and shows some analogy with what is seen in 
the Ophioglossaceae and Osmundaceae. 
