68 Lady Isabel Browne. 
abundance by Professor Thomas (42) in which the sporophylls 
showed repeated dichotomy, accompanied by the presence of a 
stalked sporangium at the angle of a dichotomy, also suggest 
reduction from a more compound sporophyll. Dr. Scott claims 
that such repeatedly dichotomous sporophylls “ are so frequent as 
clearly to fall under the head of normal variations ” (4). He regards 
them as fatal to a near affinity to the Lycopods and as strong 
support of a relationship to the Sphenophyllales. Other abnor¬ 
malities have been reported by Miss Sykes which seem to favour 
the axial nature of the synangium and its pedicel (39) ; but the 
importance to be attached to abnormalities depends chiefly on their 
commonness, unless they are of frequent occurrence they may 
probably be regarded as malformations rather than as atavistic. 
There seems no evidence that these abnormalities are by any means 
as common as those favouring the view that the synangium is leaf- 
borne. The homospory of the Sphenophyllales favours the view 
that the Psilotaceae may have been reduced from them and this 
view also receives support from the presence of what appears to be 
the reduced remains of secondary xylem in Psilotum (4), (15). But 
apart from the question of any affinity with the Sphenophyllales 
and in support of the synangium being leaf-borne Professor Bower 
has confirmed (5) Graf Solms Laubach’s observation that the 
synangium arises from the upper surface of the “ sporophyll ” and is 
not terminal, though as the former points out the lateral or 
terminal position of the synangium hardly affects the question, since 
it seems just as probable that a synangium may occupy the apex of 
a leaf as of an axis. Miss Sykes the latest defender of the view 
that the synangium is axial admits its probable homology with the 
Sphenophyllaceous sporangiophore, regarding the latter also as 
primitively cauline. She suggests that the series of forms, Spheno- 
phyllum Dawsoni, Palceostachya, Calamostachys, constructed by M. 
Lignier to show the shifting of sporangiophore on to the axis, might 
equally well be read in the inverse order, and would then illustrate 
the gradual removal of the sporangiophore from the axis to the 
sporophyll. The fact that Palceostachya appears to be derived from 
the Calamostachys-type certainly favours this view. But the origin 
of the sporangiophore trace of C alamo stachys, shown in her text- 
figure 13 b (39) from the same point as the bract-trace is somewhat 
opposed to her view. Further, as pointed out in the first article of 
the present series, such a theory offers no explanation of the 
structure of Sphenophyllum fertile. If the sporangiophores are 
