ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 943 
(1.) The sporangiophore may be a branch borne in the axil of the bracts. 
(2.) It may be a leaf, which has become adherent to the whorl below. 
(3.) It may be a ventral lobe of a leaf, of which the bract is the dorsal lobe. 
(4.) It may simply be a sporangium-pedicel, which, unlike those of any other 
Cryptogam, possesses a vascular bundle of its own. 
In the last case we might compare the sporangiophore with the funiculus of an 
ovule, but such a comparison would not advance the question much, for the true 
nature of the funiculus itself is still disputed. 
That the sporangiophore is an axial structure, z.e., a branch, does not seem to us 
probable. We have seen that the vascular tissue of each pair of sporangiophores is 
given off from the bundle of a bract, and has no direct relation to the vascular 
system of the axis. Further, the bundle of the sporangiophore is to all appearance a 
single, collateral one, a fact which would ill accord with a stem-structure. 
That each sporangiophore represents an independent leaf, is a forced, though not 
perhaps an impossible view. We should, on this hypothesis, have to imagine a 
succession of alternating sterile and fertile whorls, the latter having twice as many 
members as the former; and we must further suppose every alternate internode 
to have been shortened until each fertile verticil came to be adherent to the sterile 
verticil next below. In the absence of any developmental data such speculations 
are baseless, though analogies might no doubt be found in the floral structures of 
certain Angiosperms. Another analogy might be traced with the Calamarian 
strobili. If the sporangiophores in Equisetum and Calamostachys are really leaves, 
as most botanists assume, then in the Paleostachya type, there must have been just 
such a shortening of the alternate internodes as is required by the hypothesis, in 
Sphenophyllum. The morphology of the Calamarieze is, however, itself too doubtful 
for us to employ it in order to explain that of a remote genus. 
The view that each sporangiophore is a ventral lobe of the corresponding bract is 
that held by M. Zernuer,* and is perhaps the most natural of the hypotheses so far 
considered. In this case we must suppose each leaf to have had one dorsal lobe 
(the bract) and two ventral lobes (the sporangiophores). M. ZerLLER lays great 
stress on the analogy with Marsilia, and also with Ophioglossum. Even if we 
accepted these comparisons the question would be far from settled, for the mor- 
phology of Ophioglosswm, at any rate, is itself a subject of controversy. Professor 
Bowert maintains that the whole fertile spike of Ophioglossum is homologous with 
a single sporangium of Lycopodium. If we were to apply this view to the case of 
Sphenophyllum, we should be led back to the idea that here the sporangiophore is 
nothing but the stalk of a sporangium. We do not ourselves think, however, that 
the comparison with the complex conditions in Ophioglossum throws any light on the 
much simpler case of Sphenophyllum. 
* Toc. cit., p. 37. 
+ ‘ Proceedings of the Royal Society,’ vol. 50, p. 265, 1991. 
MDCCCXCLV.—B. 6 E 
