58 
Lady Isabel Browne. 
Professor Bower has sought to bring the Ferns into relation 
with the other Pteridophyta by regarding all the phyla as primitively 
microphyllous (9). It has been pointed out above that Professor 
Lignier has brought forward good evidence that Sphenophyllales 
and Equisetales were primitively megaphyllous (28). In the case 
of the Ferns the evidence against primitive microphylly is even 
stronger. Nearly all known Palaeozoic fern-fronds are relatively 
large and compound. Professor Bower claims that the primitive 
protostelic ferns show indications of being relatively smaller-leaved 
since no gap occurs at the departure of the trace. He also claims 
that in its ontogeny the young fern passes through such a stage in 
which the trace departing from the protostelic strand leaves no gap 
(10). But, as Mr Tansley has pointed out, there can be no leaf- 
gaps in a solid stele ; thus the absence of gaps in young plants, 
still possessing a protostelic cylinder, affords “ .... no presumption 
whatever of derivation from a microphyllous type” (41). In support 
of Professor Bower’s contention it should, however, be noted that 
in the evolution of the Osmundaceae there seems to have been an 
increase in the importance of the leaf compared to the stem, for in 
the older Osmundaceae with tubular steles the departing trace seems 
to have left no gap, while in the later forms such gaps occur (25). 
This is, however, an isolated instance and there is nothing to prove 
that even in the Osmundaceae the leaves were primitively small or 
simple. 
But while a comparison of the vegetative organs of the Ferns 
with those of the older Sphenophyllales and Equisetales seems 
legitimate, it is hard to harmonize their sporangiferous members. 
Professor Bower makes of the Ophioglossaceae an independent 
phylum ; he holds: ( a ) that their spike arose by the septation of a 
sporangium of the Lycopod type; and ( b ) that the sorus of other 
Ferns was also derived, though independently of the Ophioglossaceae, 
by septation from a single sporangium ; the synangial state, on his 
view, represents an intermediate condition, in which the walls 
separating the loculi are septa (6), (7). 
In seeking to prove the homology of the Ophioglossaceous 
spike and the Lycopod sporangium, Professor Bower relies on the 
similarity of position, of structure and of development of the spore- 
producing parts and on comparisons of gametophyte and gametangia, 
embryology and anatomy of the sporophyte in the respective phyla, 
and on the intermediate nature of the Psilotaceous synangium (6). 
It is surprising that Professor Bower should write that owing to its 
