322 ' STUDIES IN FOSSIL BOTANY 



leaf, must have been dimorphic, for the branched rachis 

 associated with the sporangia shows no signs of a lamina. 

 We know, from numerous specimens preserved as 

 impressions, that dimorphism was an exceedingly- 

 common phenomenon among the Ferns and Fern-like 

 plants of the Carboniferous period. As to the form of 

 the leaf, either sterile or fertile, beyond the fact that it 

 was a compound one, we have no direct evidence from 

 the silicified specimens. 



Pear-shaped sporangia, with a very broad and 

 extensive annulus, are commonly found associated with 

 Z. bibractensis and Z. corrugata in the petrifactions of 

 the English Lower Coal-measures, and in all probability 

 represent the fructifications of those species. 



M. Grand'Eury described, under the name of 

 Schizopteris, specimens from the Coal-measures of the 

 Loire, which are related to the structural specimens 

 we have been considering. One of the forms described 

 by Grand'Eury, Schizopteris pinnata, is a large bipinnate 

 frond, with an apparently fleshy rachis, bearing small 

 flabelliform and laciniate leaflets on its ultimate sub- 

 divisions. The author also described a fertile frond 

 {Schizostackys frondosus) very similar to the former, but 

 bearing tufts of elongated sporangia in the place of 

 the laciniate leaflets of the sterile Schizopteris} The 

 arrangement, form, and size of these sporangia agree 

 very closely with the characters of those described by 

 Renault in his Zygopteris. The structure of the Schizo- 

 stachys sporangia is to some extent preserved, and 

 the spores are visible in their cavities. The agreement 



1 Grand'Eury, Flore carbonifere du Difartement de la Loire, 1877, 

 pp. 198-203, Plate xvii. 



