434 COENOPTERIDEAE [CH. 



compound leaf. The resemblance of the synangium of Diplo- 

 labis to that of Kaulfussia (fig. 245, C) is not shared in an 

 equal degree by the sporangia of Stauropteris, which are in 

 some respects comparable with those of the Ophioglossaceae. 

 In the Zygoptereae, or at least in the case of such fertile fronds 

 as are known, and in Botryopteris (fig. 319), the sporangia occur 

 in groups, and the pedicel of each sporangium is supplied with 

 vascular tissue as in Helminthostachys. Another characteristic 

 of the sporangia of the extinct types is the possession of an 

 annulus several cells in breadth, a peculiarity which supplies a 

 point of contact with the Osmundaceae. In the sporangia of 

 Kidstonia we have a similar though not an identical type (fig. 256, 

 E, p. 340). So far, then, as the evidence afforded by sporangial 

 characters is concerned, it points to comparison with the 

 Ophioglossaceae, the Osmundaceae, and the Marattiaceae. 

 When we compare the steles of the stems we find a wide 

 range of structure. All the genera agree in being monostelic ; 

 in TubicauUs and Grammatopteris the protoxylem is exarch, 

 in Botryopteris it is internal, while the foliar strand of 

 Stauropteris and the stele of Ankyropteris corrugata are 

 mesarch. The axillary branching of species of Ankyropteris 

 suggests comparison with the Hymenophyllaceae. 



The investigation of the vascular system of the petioles has 

 afforded results which in the hands of P. Bertrand have led to 

 conclusions in regard to inter-relationships. We must, however, 

 not overlook the danger of attributing an excessive importance 

 to this single criterion and of neglecting the facts of stem 

 anatomy. 



I. Botryoptereae. 



Grammatopteris. 



Renault instituted this genus for petrified stems from the 

 Permo-Carboniferous beds of Autun. Grammatopteris Rigolloti^, 

 the type-species, is represented by a fragment, 12 — 15 mm. in 

 diameter, surrounded by crowded petioles characterised by a 

 vascular strand in the form of a short and comparatively broad 

 1 Kenault (96) A. p. 46, PIb. xxx. xxxi. See also Tansley (08) fig. 2, p. 13. 



