944 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
The chief objection to the simple view that the whole sporangiophore is nothing 
else than the pedicel of a sporangium, is the absence of any analogy among 
Cryptogams for such a great elongation and high differentiation of that organ. We 
have thought it best to state briefly the views which appear to us to be possible. 
We make no attempt to decide between them, and indeed regard the question as 
insoluble, in the absence alike of developmental facts and of satisfactory material 
for comparative study. We prefer to leave the whole question open, and, provision- 
ally, to speak of the sporangiophore as a pedicel simply, without prejudging its 
possible homologies. 
Our knowledge of the organization of Sphenophyllum is now fairly complete. We 
have not, it is true, been able ourselves to say anything as to the structure of the 
roots, nor to give any detailed account of the leaves. Considerable information on 
these points, as regards other species of the genus, will however be found in the 
works of M. Renavtt, cited above. But though Sphenophyllum is now, for a fossil 
plant, very thoroughly known, it still seems to us impossible to determine its 
affinities. That it is a vascular Cryptogam there can be no doubt, nor has this been 
questioned by any modern writer. Among the vascular Cryptogams, Sphenophylluin 
must rank as one of the most highly organized genera, on account both of the great 
histological complexity of its vegetative organs, and of the peculiar morphology of its 
fructification. However we may interpret the latter, it certainly has a highly 
specialized character. In fact Sphenophyllum affords yet another example of a 
Carboniferous Cryptogam, which, so far from representing a primitive type, is in many 
ways more elaborately modified than any recent forms. 
It is not surprising that the most various systematic positions have been assigned 
to the genus by different authors. For example, ScHenK, Van TreGHEM, and 
others, have placed it near Lycopodiaceee ; Stur refers it to Calamariee, RENAULT 
to Salviniaceze, while ZEILLER has recently traced a relationship, on the one hand, to 
Marsiliaceze, and on the other to Ophioglossee. Mr. Kipston thinks that “ the 
Sphenophylla form a peculiar group of plants, which, though standing close to the 
Lycopods, cannot be included with them, but must be placed in a class by them- 
selves—the Sphenophyllez.”* Count Sorms-Laupacu also places these plants in a 
class of their own, thinking it best “to renounce for the present all forced attempts 
at classification, and to regard the group as suz generis, as standing by itself, and 
independent.”t ‘lo this cautious view of the matter we give our adhesion, until 
additional forms shall be discovered, which may link on the genus to other families. 
The chief characters which have to be taken into account, seem to us to be these: 
(1) the jointed axis, with superposed verticils of leaves ; (2) the centripetal triarch or 
hexarch xylem, without a pith ; (3) the structure of the strobilus, especially the mode 
in which the sporangia are borne, and the relation of their pedicels to the bracts. 
* Loe. cit., p. 61, 
+ ‘Fossil Botany,’ p. 35-4. 
