55 
Inter-relationships of the Phyla. 
The question whether the simple relation of the Lycopodial 
sporangium to its sporophyll is primitive or due to reduction is a 
very difficult one. Dr. Scott remarks: “ The analogy of the 
Psilotales rather suggests the latter alternative, and all comparative 
morphology teaches, how often progress consists in simplification ” 
(34). The same botanist points out, in a foot-note, that the 
parenchymatous outgrowth bearing the sporangium in Spencerites 
might conceivably be the last relic of the ventral sporangiophore of 
Sphenophyllales though no trace of vascular tissue has been found 
in it. Miss Benson has recently reasserted the view that the 
Lycopod sporangium with its stalk represents a reduced sporangio¬ 
phore. She gives diagrams of an undescribed Carboniferous 
Lepidostrobus , which she calls Lepidostrobus Mazocarpon ; the sterile 
pad of tissue, present in many Lepidostrobi, is here much developed 
and projects into the sporangium. Miss Benson adds that the 
divergence of the elongated tapetal cells abutting on the archesporium 
leads to a split in the median plane of the megasporophyll and that 
this somewhat suggests a multiple origin of the sporogenous mass. 
She compares these sporangia to those of the genus Mazocarpon ; 
here there is a still larger amount of sterile tissue projecting into 
the sporangia; according to her figures the upper part of the 
sporangial wall is also lined by about three to five layers of sterile 
tissue, between which and the sterile tissue projecting from below, 
there is, in the median region, only a narrow space. Miss Benson 
says : “ The tetrads are here arranged along the two sides and the 
space around them was filled with tapetal cells which have perished. 
One seems to see in this sporange an explanation of the saddle form 
of many of the ‘ sporangia ’ of recent Lycopods, accompanied as 
such a form is by a well developed ‘ archesporial pad ’ . . . . It 
would be a very natural sequence that the sporogenous regions of a 
single sporangiophore should become confluent, and the gradual 
reduction of the sterile tissue to a mere ‘ archesporial pad ’ and 
pedicel would next follow ” (2). On this hypothesis the Psilotaceous 
synangium would presumably exemplify one of the antecedent 
stages in the reduction of the sporangiophore with its free sporangia 
to the Lycopod “ sporangium,” in which the fusion of sporogenous 
masses is complete. Professor Bower also regards the Lycopod 
sporangium as the homologue of the synangium of the Psilotales, 
but he takes the opposite view to Miss Benson and regards the 
sporangia constituting the synangium of the latter phylum as the 
loculi of a septate sporangium (5). Miss Benson’s figures of 
