BOTRYOPTKRIDEAE 499 



B.R. (Fig. 269), a condition comparable with that seen in a modern 

 Osmunda : but in other cases the axis was more elongated, and the 

 leaf-arrangement less dense, as in Zygopteris Grayi, where there is a two- 

 fifths divergence (Fig. 270), or in species of Botryopteris, where the 

 leaf-arrangement appears to have been more lax still. From the axis, 

 which was often thin in proportion to the more robust leaves which it 

 bears, sprang also numerous adventitious roots (r, Fig. 270): these seem 

 to have acted as oblique prop-like supports where the axis was elongated. 

 In some cases at least axillary buds arise in the axils of the leaves, very 

 much as they do in some modern Hymenophyllaceae. 



The leaves themselves were repeatedly branched, the pinnae arising 

 alternately from the rachis, and being themselves further branched. 



FIG. 269. 



Botryopteris Rigolloti, B. Renault. Transverse section of the central part of a stem : 

 within the axis lies the solid vascular cylinder (a) surrounded by a continuous band of 

 bast ; i he cortex (/>) is traversed by vascular strands (c) passing to the leaves ; d~ petioles 

 surrounding the stem. Communaux de Saint-Martin. (After Renault.) 



Aphlebiae have been described on the leaves of both British and 

 Continental specimens. The leaves were of a finely divided Sphenopterid 

 type: in the sterile leaves the ultimate segments widened out into fan- 

 like expansions : in the fertile regions the segments remained narrow, and 

 upon the ultimate branchlets the large, pear-shaped sporangia were borne 

 in distally directed tassels, or in some cases solitary. 



Fortunately the internal structure is fairly well known in several distinct 

 types of the family, and generic characters have been based upon the 

 differences recognised. The simplest, and for comparative purposes pro- 

 bably the most important type, is that shown by Grammatopteris Rigolloti 

 (Fig. 269), where there is in the axis a solid xylem-core, with the smallest 

 tracheides at the periphery. Round this is an exiguous phloem, and a 

 broad outer cortex. In the latter are embedded numerous leaf-trace 

 bundles on their way out to the crowded leaves : their structure is simpler 

 than in others of the family, the prominent feature being a strap-shaped 



