Margaret Benson 
84 
Stauropteris (no stem has so far been discovered) and the fertile 
branching system of axes of some members of the Psilophytales 
seems to add a still fuller justification for the view that the “frond” 
of Ferns has been evolved from a branching thallus by the appen- 
dicularization of a system of branches whether fertile or barren. 
For such leaves the term “Meriphylls” is here proposed, as Jeffery’s 
“Megaphyll” includes the Meiophyll. 
The soromata were involved and with the new source of nutrition, 
which the cladodification of the system of axes supplied, are found 
to have themselves undergone elaboration into synangia and sori. 
Segmentation of the synangium followed first into equivalent 
parts as in the Simplices and later along so many different lines 
of descent, as shown by Bower, into the Mixtae type of sorus. In 
no case do we find an exception to the law that among the Meriphylls 
the soromata are “taken up” upon the leaves as the writer expressed 
it in the 1908 “ Sporangiophore ” paper. In contrast to this we note 
that among the Sphenopsida the soromata more or less retain their 
independence of the leaf even though the vascular supply may be 
given off from the axis together with that of the leaf as in the cone 
of Calamostachys. 
Relative antiquity of strobilus formation. 
Turning now to a consideration of the relative antiquity of 
strobilus formation in the three groups Haplophylls, Meiophylls and 
Meriphylls respectively, we see that strobilus formation occurred 
at a vastly earlier epoch in the Haplophylls and Meiophylls than 
in the Meriphylls. In fact it has never been recorded among the 
Filicales which are the only Cryptogamic representatives of the 
Meriphylls and was only attained relatively late by their seed-bearing 
congeners. 
This fact may be correlated with the limitation of the branching 
of the originally appendicularized constituents forming the “cone 
scale”—only axes of the second or third order obtaining. In the 
Psilotales it is possible that the very frequent anomalies of Tmesi- 
pteris indicate that the telescoping down of the soromata-bearing 
axes to that now regarded as the normal may be comparatively 
modern. To sum up: in the character of the leaf, in the insertion 
of the soroma and in the date of strobilus formation we have 
characters distinguishing three groups of Vascular Cryptogams. 
Let us now turn to the Spermophyta. 
There is no group of seed plants with a universally uninerved 
leaf constructed on the plan of the Haplophylls. 
