470 OOENOPTERIDEAE [CH. 



Valenciennes. The sporangia are large, ovoid, and sessile ; the 

 annulus (fig. 309, D) has the form of a complete vertical band 

 several cells in breadth: five to ten sporangia are grouped 

 round a receptacle. Zeiller describes two species as Spheno- 

 pteiis (Corynepteris) coralloides Gutb. and 8. (Corynepteris) 

 Essinghii And. ; in both the fronds are quadripinnate and bear 

 aphlebiae at the base of the pinnae. The former species is 

 recorded by Kidston^ from the South Wales Coal-field. A 

 single pinnule of C. coralloides is shown in fig. 309, C. Potoni6^ 

 refers this frond to his genus Alloiopteris : the portion of a 

 pinna represented in fig. 354 G shows the characteristic modified 

 pinnule next the rachis. Zeiller draws attention to the occur- 

 rence of two parallel lines on the rachis of a specimen of 

 Corynepteris coralloides which he figures', and suggests that 

 these may indicate the existence of an H -shaped form of 

 vascular strand like that of Etapteris and Ankyropteris. The 

 sorus of Corynepteris is comparable with that of the Marattia- 

 ceae, but the broad annulus is a difference which suggests 

 affinity to Etapteris. The sorus is similar to that in Diplolahis 

 (fig. 309, A), but in that genus the sporangia are exaimulate. 



The vascular axis in the stems of different members of the 

 Coenopterideae assumes a variety of types. In Botryopteris 

 antiqiia the xylem forms a solid protostele in which no proto- 

 xylem strands have been recognised ; in other species, e.g. 

 B. ramosa, the cylindrical stele is similar to that of Tricho- 

 manes radicans (Hymenophyllaceae) in the more or less central 

 position of the protoxylem. In Botryopteris forensis the 

 protostele is said to be exarch. The probability is that the 

 central Botryopteris type is the endarch protostele, a form of 

 vascular axis which may be regarded as primitive. The leaf- traces 

 of the Lower Carboniferous Botryopteris antiqua are simple 

 oval strands differing but slightly from the cylindrical stele 

 of the stem. In the Upper Carboniferous British species the 

 petiolar vascular strand has become more specialised and 

 farther removed from that of the stem; in B. furensis the 



1 Kidston (94). « Potoni6 (02) p. 492. 3 Zeiller (88) A. PI. x. 



