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XLV] VOLTZIA 289 



VOLTZIA. Brongniart. 



Brongniart 1 instituted this genus for foliage-shoots from the 

 Bunter sandstones of the Vosges, the name being chosen in com- 

 memoration of Voltz; he compared the branches with those of 

 Araucaria excelsa but added that the cone-scales bore three ovules. 

 The leaves show considerable variation even on the same axis, 

 a feature shared with Walchia and Ullmannia: the megastrobili 

 are characterised by a lax disposition and the fan-like, lobed or 

 crenulate form of the megasporophylls, which in the best preserved 

 type, V. Liebeana (fig. 748, C F), bear three ovate seeds on the 

 upper surface. Many authors compare the Triassic genus with 

 members of the Taxodineae, e.g., Cryptomeria, and the Araucari- 

 neae: wood of the Araucarian type has been referred to Voltzia 

 though without proof of connexion with the vegetative shoots. 

 Gothan 2 , who favours a Taxodineous alliance, points out that 

 wood associated with Voltzia has Araucarian pitting on the 

 tracheids, though he adds that the occurrence of typical Araucarian 

 pitting in stems possessing other characters foreign to the recent 

 Araucarineae justifies the conclusion that the presence of alternate 

 polygonal pits on the tracheids is not necessarily proof of Arau- 

 carian affinity. An examination of some carbonised fragments 

 attached to cone-scales of V. Liebeana in the British Museum from 

 Gera revealed the occurrence of uniseriate pits both separate and 

 in contact with one another. It is probable that Voltzia is related 

 to the Araucarineae though in what degree is uncertain. A recent 

 view 3 that Voltzia affords an illustration of a generalised type 

 combining Araucarian and Abietineous features is in part based 

 on an assumption that the cone-scales are double like those of the 

 Abietineae. That the genus is a generalised type is probable, 

 but the data are insufficient to warrant any definite statement as 

 to which Coniferae are the nearest allies. The range of the genus 

 is difficult to define : if we include the species V. keuperiana, also 

 Heer's genus Leptostrobus, the geological range extends from the 

 Permian to Middle Jurassic floras. The typical species are charac- 

 ristic of Permian and Lower Triassic rocks. The similarity in 

 habit of Walchia, some species of Ullmannia, and Voltzia renders 



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Brongniart (28) p. 448, Pis. xv. xvn. 2 Gothan (10) p. 31. 



3 Holden, R. (13). 



s. iv 19 



