ZYGOPTERIS 319 



is ranged in regular radiating series, and has all the 

 appearance of a secondary tissue, precisely as in a 

 recent Botrychium. The stele, in fact, is related to that 

 of a Zygopteris, as the stele of Botrychium is related 

 to that of Ophioglossum. Botrychioxylon, which may 

 eventually have to be included under Zygopteris, at 

 present affords the only instance of secondary growth 

 of the wood among the Botryopterideae. 



We now come to the interesting subject of the 

 fructification of Zygopteris, our knowledge of which is 

 almost entirely due to the researches of M. Renault. 



The evidence of identification, if not absolutely 

 conclusive, is at least sufficient to leave no reasonable 

 doubt. The sporangia (see Fig. 1 1 9) occur in groups, 

 often of considerable extent. They are elongated, 

 slightly curved sacs, thickest towards the distal end, 

 and of relatively large size, reaching a length of 2.5 

 mm. and a diameter of 1.3 mm. Each sporangium 

 is attached by its thin end to a short pedicel ; the 

 pedicels are united in little tufts, three to eight in each 

 tuft, on a common peduncle (Fig. 1 1 9, 1 and 2). The 

 whole mass is traversed by fragments of a branched 

 rachis, on which the peduncles were no doubt borne. 

 In some sections of the rachis the characteristic H-like 

 form of the Zygopteris bundle is clearly shown ; " it is, 

 then," to quote the words of M. Renault, " very probable, 

 if not certain, that these masses of sporangia constitute 

 the fructifications" of Zygopteris} 



The wall of the ripe sporangium consisted of at 



1 Flore fossile cTAuttm et cTEpinac, Part ii. p. 43. The original 

 discovery was made by M. Renault as early as 1876. " Veg. silicifies 

 d'Autun," Ann. des sci. nat. (Bot.), ser. vi. vol. iii. 



