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THE GROUPING OF VASCULAR PLANTS 
By MARGARET BENSON 
I N 1908 the writer reviewed in this journal (7, p. 143) the range 
of the sporangial (especially the microsporangial) apparatus of 
Vascular Plants. The suggestion was made that all the types borne 
on the sporophyte could be homologized and that, by accentuating 
the resemblances between synangia, sori, sporangiophores, half 
anthers and seeds, we should be better able to concentrate attention 
on their probable origin. 
As it has been found impossible to extend the denotation of the 
term “ sporangiophore ” to cover so many differentiated types it will 
be clearer to employ a new term and that of “soroma” is now sug¬ 
gested. By “soroma” we mean the sporangial apparatus of the 
vascular plant plus the receptacle or stalk. The soroma of the 
Psilophytales already showed a considerable range of structure but 
it agreed in being borne on an axial-like arm of the thallus or plant 
body, and in being radially symmetrical. In the case of Horned 1 
the soroma shows a flattened apex and a central columella and on 
several occasions was found to branch. 
These recent revelations as to the structure of the earliest known 
land plants have heightened the interest in the sporangiophore 
(soroma) as we can now interpret its stalk (receptacle) as homologous 
with the primal type of axis of radially symmetrical plants indis¬ 
tinguishable from Thallophyta. Such cases as Sphenophyllum fertile 
and the anomalous branching systems of the soromata (synangia) 
of Tmesipteris fall at once into line with the structures found in 
the Old Red Sandstone plants. Mrs Thoday’s theory 2 of the axial 
nature of the pedicel of the so-called “sporophyll” of Tmesipteris 
is much strengthened and the two leaf-like lobes can now be safely 
interpreted as cladodified branches of this axis. Such primitive uni- 
nerved leaves may be called “ Haplophylls.” In this discussion we 
will accept the view that Haplophylls are also characteristic of the 
great group of Lycopodiales although in some species of Sigillaria 
we find a variant. 
1 Kidston and Lang, Trans. Roy. Soc. Edin. 52 , Part III, p. 614. 
2 Sykes, “Anatomy and Morphology of Tmesipteris .” Ann. Bot. 22 , 1908, 
p. 81. 
