6 3 
Inter-relationships of the Phyla. 
evidence to show that the number of these compound leaves in a 
whorl was primitively three. Professor Lignier takes a similar view 
of the sporophyll of the Sphenophyllales, and believes that even 
where most often divided, the sporophylls of this phylum represent 
lobes of three more highly compound fertile leaves which have 
become secondarily free from one another in a way analogous to 
that described above. Thus we gain the conception of a small 
number of relatively large compound sporophylls not unlike fronds, 
especially if we bear in mind Professor Lignier’s contention that 
the whorling of the leaves of the Sphenophyllales presumably 
caused a certain reduction in their size (28). In seeking for ferns 
from which to derive these Sphenophylls with frond-like sporophylls, 
Professor Lignier selects the group of fossils known as Archaso- 
pterideae (29), refusing to recognize Mr. Kidston’s reasons for 
regarding these as Pteridosperms rather than as ferns (23). The 
prevalence of the Pteridosperms, or at least of the Cycadofilices 
(for the latter may not all have been seed-bearing), in the older 
deposits in which fern-stems relatively rare, speaks strongly for Mr. 
Kidston’s view; but even if the latter be accepted it is not unlikely 
that these older Cycadofilices or Pteridosperms may have inherited 
from the ancestor they presumably share with the older Perns certain 
primitive soral characters. Thus it is probable that the sporangia 
of the ferns were primitively, as Professor Lignier contnds, relatively 
large and exannulate, and they may have been inserted singly or in 
small numbers at the ends of the veins (28), (29). To these supposed 
primitive ferns Professor Lignier applies Mr. Arber’s name of 
Primofilices (as being a wider term than Archaeopterideae); but he 
uses it, as he points out, in a very different sense, since he regards 
the Primofilices as the group that gave rise not only to the recent 
ferns, but to the Pteridosperms and his Articulatae (Equisetales and 
Sphenophyllales). The sporophyll of the Sphenophyllales is then 
regarded by Professor Lignier as the lobe of a frond; its divisions 
as lobes of the second or higher orders and as pinnules ; of these 
pinnules the median sterile one alone is supposed to remain laminar, 
while the two lateral sporangiferous ones, reduced to a midrib 
bearing one or two terminal sporangia, are regarded as displaced on 
to the adaxial surface where they constitute the sporangiophores. 
In support of such shifting, which sometimes causes the sporangio¬ 
phores to assume the appearance of an independent whorl super¬ 
posed to the sterile one, Professor Lignier claims that the bundles 
supplying the sporangiophores are inserted laterally on the bundle 
