lilNNEAN SOCIETY OF LO>'DO:!f. 55 



Botrvopteridea; constitute one family of the Priiiiofilices, aud 

 others will prohably be distinguished iu the near future. 



The origin of the LeptosporangiatcTe from the Primofilices is clear. 

 This group began to differentiate at the close of the Palteozoie 

 period. Possibly some of the Sphenopterid fronds of the Carboni- 

 ferous aud Permian rocks, bearing annulate sporangia, were the 

 earliest offshoots in this direction. In the true Mesozoic floras 

 (Ehpetic, Jurassic, and Wealden) the various families became 

 marked out, and there is abundant evidence that the Lepto- 

 sporangiatse then formed one of the dominant or ruling types of 

 Mesozoic vegetation. 



On the other hand, the question may well be asked, Is there any 

 trustworthy evidence of the existence of the Eusporangiatae in 

 either the Palaeozoic or truly Mesozoic floras ? In neither is there 

 any evidence at all of the Ophioglossacea?, and the only instance 

 of possible Mesozoic Marattiaceous fronds with which I am 

 acquainted are three in number, and all of EbiBtic age. In two 

 species of Tcenioptcris (including the typical Rhaetic species 

 T. Jlilnstej'i) sporangia, resembling those of the modern Marattia, 

 have been found on certain fronds while in Dano'opsis, another 

 related genus, the synangia more closely resemble those of Dancea. 

 The suspicion is not wanting, however, that the fi'onds of Tamio- 

 jiteris may have been those of a Cycad rather than a Pern. 



In the Palaeozoic rocks, we find a plexus of fronds of the 

 Sphenopterid and Pecopterid type, bearing exannulate sporangia, 

 arranged independently in the sorus, or united to form synangia. 

 These have been generally regarded as of Marattiaceous aftiuity. 

 The great difficulty, at the present moment, is to decide as to the 

 true nature of these fronds. Did they belong to true homosporous 

 Ferns, or were they the male fronds of Pteridosperms ? On the 

 present evidence, I am inclined to think that a large number, 

 though not necessarily all, will eventually pi'ove to fall under the 

 latter category. "We already know that one Pecopteris (P. PlucJc- 

 eneti), though not a very typical member of the genus, belonged 

 to a Pteridosperm. Also the male frond of the Benuettiteae, a 

 group descended from the Pteridosperms, is known to have borne 

 sporangia not unlike those of the Palaeozoic Pecopterids and the 

 modern Marattiacea;. 



The anatomy of the tree-fern, Psaronlus, affords the most trust- 

 worthv evidence, at preseut, of the existence of the Eusporanf/iatce 

 in Palaeozoic times ; though there would appear to be little to 

 indicate that this group ever attained to the position of a dominant 

 or ruling type in either the Palaeozoic or truly Mesozoic floras. 



