36 
Lang. — Studies in the Morphology and 
statement holds for the other phyla, but it does not seem to apply without 
considerable modification to the Filicales. It seems clear from Campbell’s 
figures that the primary root is endogenous and practically median in the 
Marattiaceae even when, as in Danaea , a suspensor is present. What we 
know as to the initiation of the primary root in Helminthostachys suggests 
that the same holds here also, though the root subsequently appears lateral 
owing to the great development of the foot and the change in direction of 
the axis of the shoot. The direct continuation of the axes of the shoot and 
primary root is very striking in Lyon’s figure of Botrychium obliquum. 
It has been further pointed out above that the first root in Helmintho- 
stachys occupies a different position, relatively to the dorsiventral axis, from 
that occupied by the later roots, and this difference may have its explana- 
tion in the original polar position of this root as the continuation backwards 
of the primary axis of the plant. In this respect the relations in Helmin- 
thostachys appear closely comparable to those shown for the dorsiventral 
rhizome of the young plant of Polypodium vulgare in a figure by 
Professor Bower. 1 There is thus some evidence for regarding the first root 
in the Filicales as different from the succeeding roots and potentially a main 
or tap-root. It would be comparable in not giving rise to the whole root- 
system to the primary root of a Monocotyledon. The position of the primary 
root-apex relatively to the suspensor in such a plant as Danaea is comparable 
to what is the rule in Gymnosperms, Dicotyledons, and Monocotyledons. 
That such resemblances in the primary arrangement of the organs 
should be traceable between the Spermaphyta and the more primitive 
Filicales is of some interest and importance. It seems possible that the 
presence of a suspensor and the relative position of the organs of the 
embryo (including the terminal root with its apex directed towards the 
suspensor) may be characteristics of the higher plants that have persisted 
from the condition present in a filicineous ancestry. Proof is impossible in 
such a question, but it seems justifiable to state this view without asserting 
it to be the only or the complete explanation of the facts. 
Summary. 
i. The embryo of Helminthostachys extends down into the prothallus 
before segmentation takes place. The first two walls are transverse. Of 
the row of three cells, the one next the archegonial neck becomes the upper 
tier of the suspensor ; it may remain undivided or become divided up into 
smaller cells. The next cell forms the second tier of the suspensor and 
becomes divided up into cells. The embryo proper is formed from the 
terminal cell of the filament. 
3. The embryo proper is at first straight, continuing the line of growth 
1 Land Flora, p. 214, Fig. no. 
