ASTEROCHLAENA 325 



from the Carboniferous and Permian, has a stem- 

 structure (in A. Decaisnei, Ren.) almost identical with 

 that of Zygopteris Grayi, but the petiolar bundle has 

 quite a different shape, forming a strongly incurved arc, 

 concave towards the parent stem. Asterochlaena, rang- 

 ing from the Upper Devonian to the Permian, has a 

 very deeply lobed stele, with the forked arms much more 

 prominent than in Zygopteris (see Fig. 120). The 

 protoxylem, in a section shown me by Mr. Kidston, 

 appeared to be sunk below the projecting corners of 

 the wood. The petiolar bundles are lunulate, with the 

 concavity directed outwards or inwards, according to 

 the species. Their relation to the stele has not yet 

 been fully cleared up, and the interesting genus much 

 needs reinvestigation. 



B. Botryopteris Group 



3. Botryopteris. — We will next consider Botryopteris, 

 the type-genus of the family, and very distinct from the 

 Zygopteris group. Our knowledge of this genus was, 

 in the first instance, based on M. Renault's species, B. 

 forensis, which that author described very thoroughly, 

 though he had only a single specimen of the stem to 

 work with. 1 Subsequently, however, it turned out that 

 certain English Coal-measure fossils, which fortunately 

 occur in considerable abundance, must be placed in the 

 same genus. Hence we are able to supplement the 

 descriptions of the original discoverer by observations 

 on our own, specifically distinct, examples. Anatomic- 

 ally, Botryopteris shows a decidedly simpler structure 



1 Cours de bot.foss. vol. iii. chap. viii. ; Ann. des sci. nat. (Bot.), ser. 

 vi. vol. i. 1875 ; Flore fossile d'Autun et d'Epinac, Part ii. p. 33. 



