282 STUDIES IN FOSSIL BOTANY 



Another genus, Scolecopteris, also belonging to 

 Pecopteris according to its foliar characters, has the 

 same arrangement as in Asterotheca, but the synangia 

 are stalked, and the sporangia long and sharply pointed 

 at the apex. Fructifications of Scolecopteris have been 

 found in a silicified condition, and their structure has 

 thus been more thoroughly investigated than is usually 

 possible. In one species, S. polymorpha} the large 

 tripinnate fronds bear two long rows of sori on the 

 lower surface of each pinnule. The sporangia in each 

 sorus are four in number ; they are free for the greater 

 part of their length, which reaches about 4 mm. ; 

 at their base they are attached to the surface of the 

 pinnule, and on their inner side to a short receptacle, 

 not more than one-third as long as the sporangia (see 

 Fig. 1 10). The receptacle is described by M. Renault 

 as having a cruciform transverse section, each arm of 

 the cross corresponding to one of the four sporangia 

 constituting the synangium (see Fig. 1 1 o, A, sp). Each 

 of the long, pointed sporangia has a wall with thickened 

 cells on its free outer surface, but on the inner side the 

 wall is thin. It is probable that this unequal thickness 

 of the wall caused the dehiscence of the sporangium on 

 the inner side, and thus worked in the same way as the 

 annulus of ordinary Ferns. The margins of the pinnule 

 were incurved, so as to partly cover in the sori. Another 

 species of Scolecopteris, S. elegans, was investigated many 

 years ago by Strasburger. 2 The sporangia are here 

 smaller, and there are often five in each sorus. 

 Towards the base they are confluent with one another, 



1 Renault, I.e. p. 116, PI. 20, Figs. 1-10 (Pecopteris polymorpha). 

 2 /enaer Zeitsckrift fur Naturwissensehaft, vol. viii. 1874. 



