170 PACHTPTEEIS. 



vel uninerviis, basi constrictis nee rachi adnatis." ' He notes 

 the form of the pinnules, which are never lobed, and the absence 

 of veins as characteristic features. Brongniart and many other 

 authors place Pachypteris among the ferns, but in 1845 linger 2 

 included the genus among the "Cycadacese dubise," and Andrae 3 

 regarded it as a member of the Taxinese. Zigno instituted the 

 genus Dichopteris for ferns having bipinnate fronds characterized by 

 a stout rachis bearing linear pinnae with short lanceolate or ovate- 

 segments traversed by several veins. A specimen figured by thi& 

 author as a portion of a fertile frond of Dichopteris microphytta, 

 Zigno, 4 has been accepted by Schimper and others as definitely 

 settling the fern-nature of the genus. This critical example 

 I regard as a piece of a fertile frond of Todites ; the pinnules 

 agree in shape and in the arrangement of the sporangia with 

 the fertile segments of Todites Williamsoni (Brongn.). 5 In 1873 

 Saporta proposed a new genus Scleropteris for several imperfectly 

 known species previously referred to Pomel's genus Laxopteris, 

 to Sphenopteris, Dichopteris, and Pachypteris? It is probable that 

 more than one generic type of plant is included in Saporta's 

 genus ; some of the species are undoubtedly ferns, while others, 

 formerly referred to Pachypteris or Dichopteris, may possibly be 

 Cycadean. In placing Pachypteris among the ferns of doubtful 

 affinity, it is not intended to imply that the evidence available 

 renders that position in any sense established. The argument 

 advanced by Brongniart against Unger's reference of Pachypteris 

 to the Cycads, that no Cycad is known with bipinnate fronds, 

 cannot bo maintained; in the Australian genus Bowenia we have 

 a well-known instance of a Cycad with bipinnate leaves, and it 

 is very probable that this form of leaf was not infrequently borne 

 by stems having the structure of Cycads. Recent research has 

 thoroughly established the closest affinity between Cycadean and 

 Filicinean types in the Palaeozoic epoch, and there is evidence that 

 during the Mesozoic period the distinction between Ferns and 



1 Brongniart (28 2 ), p. 166. 



2 linger (45), p. 165. 



3 Andrae (53), p. 43. 



1 Zigno (56), pi. xv. fig. 5. 



5 Vide ante, p. 90. 



6 Saporta (73), p. 364. 



