406 SPHENOPHYLLALES. A. SPHENOPHYLLEAE 
phylls.1 These were arranged in whorls of twelve, and were superposed ; 
each consisted of three sterile lobes palmately divided, and it bore upon 
its upper surface, and inserted close to its base three sporangiophores ; 
each of these was provided with four long pendent sporangia attached to 
its peltate distal end (Fig. 223). So far as the vascular connections are 
a guide, it may be concluded that the sporangiophores are appendages 
of the branched sporophyll, and especially of its middle 
segment, since a vascular strand supplying them originates 
from the bundle which runs into the middle segment of 
the sporophyll. This strand divides then into three, 
and one branch enters each of the sporangiophores 
(Fig. 224). Thus, as Scott himself points out,? the 
course of the vascular bundles supplying the sporangio- 
phores and bracts is essentially the same in Spheno- 
phyllum and Chetrostrobus, though necessarily more 
complex in the latter. 
There can be little doubt of the fundamental 
Forked sporophyll of . . 
Sphenophylium majus, correspondence of the various types above described: 
bearing sporangiophore. £ . A a 
(After Kidston.) they all coincide in the presence of spore-producing 
parts subtended by sterile bracts arranged in whorls: 
and notwithstanding their differences in number, and in the number of 
sporangia which they individually bear, it is safe to conclude that the 
sporangiophores are homologous throughout the series. Their similarity of 
general structure to the sporangiophores of the Equisetales is most clearly 
seen in Sphenophyllum majus, or in greatly elongated form in Chetrostrobus : 
considering this in conjunction with their correspondence in function, there 
is reason also to recognise a distinct relation to the sporangiophores of 
the Equisetales. In point of position there is the difference of their being 
leaf-borne, as against fhe axial insertion of the Equisetales; in fact the 
relation to the leaf is similar to that often seen in them, but closer. 
The conclusion seems inevitable that the sporangiophore in these two 
phyla is a member of similar morphological rank, though it may in both 
phyla show some variety in its exact position. 
And here it will not be inapposite to point out in support of this view 
some features of structural similarity which exist between the Equisetales and 
the Sphenophyllales. They will be best illustrated in brief by the juxta- 
position of Scott’s two figures (compare Fig. 217 with Fig. 225). The 
former shows the transverse section of the ancient S. zzsigne from 
Burntisland, which differs from the later Sphenophylls in having a canal 
marking the position of the protoxylem at each angle of the primary wood ; 
also in having continuous medullary rays in the secondary wood, and 
scalariform tracheides in place of those with numerous bordered pits. 
Fic. 222. 
1A second specimen, belonging also to Mr. Kidston, to whom the original discovery 
was due, shows only eleven protoxylems. 
22a, pe 113. 
