OF PSILOTACEAE 147 
Sphenophyllaceae raise important questions. Among the former, Zimesipterts 
bears appendages of simple form in the vegetative region; but the fertile 
appendages are forked at their distal end, and bear on their upper surface, 
just at the point of branching, a bilocular synangium, which has a short 
stalk traversed by a vascular strand (Fig. 77). Various views have been 
propounded in order to read this body in terms of the formal morphology 
of the higher plants: for us, the suggestion would seem to suffice that 
Fic. 76. 
Spencerites insignis. Somewhat diagrammatic radial section of part of the cone, 
showing two sporophylls in connection with the axis. On the lower sporophyll the 
sporangium is shown attached at its distal end to the ventral outgrowth of the sporophyll : 
within the sporangium some of the characteristic winged spores are shown. (After Miss 
Berridge.) From Scott, Progressus rei Botanicae, vol. i. 
the plant is heterophyllous, the vegetative appendages being simple and 
the fertile branched: while to the upper surface of the branched sporophyll 
a sporangiophore is attached with vascular supply and bearing two sporangia. 
In Pstlotum the structure is the same, but the number of the sporangia 
is larger. The disposition of the parts in Sphenophy/lum majus is again 
very similar to this (Fig. 78): a synangial group of four to six sporangia 
occupies a position comparable to that of the Psilotaceae on the upper 
surface of a doubly branched appendage ; but these appendages are disposed 
