OF PSILOTACEAE 



147 



Sphenophyllaceae raise important questions. Among the former, Tmesipteris 

 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 



FK,. 76. 



Spcncerites iiisignis. 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 Mis.-. 

 Berridge.) From Scott, Progresses rci 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 Psilotitm the structure is the same, but the number of the sporangia 

 is larger. The disposition of the parts in Sphenophyllum majiis 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 



