XXIl] PTYCHOCARPUS 397 



leptosporangiate sporangia, the interpretation of structural 

 features in petrified or carbonised sporangia does not afford 

 an example of unanimity among palaeobotanical experts. 



Ptychocarpus. 



This generic name, proposed by the late Professor WeissS 

 is applied to a type of fructification illustrated by the plant 

 which Brongniart named Pecopteris unita, a species common in 

 the Upper Coal-Measures of England'^. It is adopted by Kidston 

 for fertile specimens from Radstock which he describes as 

 Ptychocarpus oblong us^, but the precise nature of the fertile 

 pinnules of this species cannot be determined. 



Ptychocarpus unita (Bvongn.*). Fig. 291, A, B. (= Goniopteris 

 unita, Grand'Eury.) 



This species has tripinnate fronds with linear pinnae bearing 

 contiguous pinnules of the Pecopteris type (fig. 291, B), 4 — 5 mm. 

 long, confluent at the base or for the greater part of their length. 

 On the under surface of the fertile segments, which are identi- 

 cal with the sterile, occur circular synangia (fig. 291, A) consist- 

 ing of seven sporangia embedded in a common parenchymatous 

 tissue and radially disposed round a receptacle supplied with 

 vascular tissue. The synangium is described as shortly stalked 

 like those of Marattia Kaulfussii (fig. 245, B', p. 320). In shape, 

 in the complete union of the sporangia, and presumably in 

 the apical dehiscence, Ptychocarpus agrees very closely with 

 Kaulfussia (fig. 245) ; but we cannot be certain that we have 

 not a collection of microsporangia simulating a fern synangium. 



A synangium closely resembling Ptychocarpus has been 

 described by Mr Watson^ from the Lower Coal-Measures of 



1 WeisB, C.E. (69) p. 94, PL xi. fig. 2. The specimens figured by Weiss bear 

 a somewhat remote resemblance to that described by Eenault (96) A, under the 

 same generic name. 



2 Kidston (91^) p. 23. ' Kidston (88) p. 350. 



4 Renault (96) A. p. 9; Zeiller (88) A. p. 162; Grand'Eury (77) A. PL viii. 

 fig. 13. 



» Watson (06). 



