290 



CONTFERALES INCERTAE SEDIS 



[CH. 



exceedingly difficult the determination of sterile branches. 

 Further, the fact that the specimens of this presumably arborescent 

 genus are usually small branch-fragments sets a limit to our know- 

 ledge of the external features of the individual plants. 



Voltzia heterophylla Brongniart. 



The examination of numerous specimens from the Bunter 

 sandstone of the Vosges led Schimper and Mougeot to include 





FIG. 748. Voltzia. A, B, Voltzia heterophylla (B, medullary cast), C F, Voltzia 

 Liebeana. (A, B, after Seward; C F after Geinitz.) 



under this name Voltzia brevifolia and V. rigida of Brongniart 1 . 

 The Triassic species Voltzia heterophylla (fig. 748, A) is the best 

 known representative of the genus: the vegetative shoots agree 

 very closely with those of Amucaria excelsa and differ but little 

 from shoots of Walchia, some forms of Ullmannia, and Pagiophyl- 



1 Brongniart (28) p. 446; Schimper and Mougeot (44) A. p. 21, Pis. i., vi. ix. 



