A. C. Seward — Tylodendron and Voltzia. 



219 



have had an opportunity of seeing the original specimens on which 

 Weiss founded his genus, and also the casts taken by Potonie of 

 medullary cavities of recent Conifers. I was at once struck with the 

 practical identity of the two sets of specimens, and felt convinced of 

 the correctness of Potonie's conclusions. 



In looking through the collection of fossil plants in the Strassburg 

 Geological Museum, I found a specimen of Voltzia heterophylla which 

 seemed to me a most interesting example of a case, in which what 

 looks like a cast of an entire stem covered with elongated leaf-bases, 

 should in reality be considered as simply a cast of the medullary 

 cavity. 



The elongated areola?, I consider, correspond to those of Tyloden- 

 dron, and represent casts of the inner ends of the primary medullary 

 rays. All that remains of the wood and 

 cortical tissues is a small amount of carbona- 

 ceous matter on either side of the central cast. 

 In this specimen of Voltzia the areolae are 

 more elongated than in Tylodendron ; but in 

 both cases we have the slit extending up- 

 wards from the lower end of the areola? 

 representing the position of the foliar bundles. 

 The Voltzia cast shows no periodic swellings 

 as in Tylodendron, nor any alteration in the 

 length of the areola? such as occurs in the 

 neighbourhood of the swollen portions of 

 the latter genus. Similar swellings and 

 accompanying variations in the length of 

 the areolae occur in casts of medullary cavities 

 of recent Araucaria at points where verticils 

 of branches are given off. The specimen 

 referred to closely resembles those figured by 

 Schiinper - from the same locality — Soulx-les- 

 Bains. The axis, which consists of an iron- 

 stained core, pi - ojects above the surface of 

 the rock ; the elongated lozenge-shaped areas 

 are not sufficiently well preserved in all parts 

 to be accurately measured ; but in Fig. 1, I have attempted to re- 

 present a few of them as correctly as possible. On each side of 

 the iron-stained axis are traces of carbonaceous matter ; some also 

 occurs here and there on the axis itself. In the Palosontographica 

 for 1886 3 Dr. Blanckenhorn figures and describes some fragments 

 of what he considers Voltzia heterophylla : these figures agree closely 

 with the specimen here described. Blanckenhorn's specimens are 

 described by him as branches from which the leaves have fallen, 

 their surfaces being covered with long leaf-cushions separated from 

 one another by furrows : each cushion has a groove extending from 

 the lower end to the middle. The close resemblance of these 



1 Schimper et Mougcot, Plantes Fossiles du gres bigarre", pt. 1, tab. xiv. etc. 



2 " Die Fossile Flora des Buntsandsteins uud des Muschelkalks der Umgegend von 

 Coniniern " (Palaeontograpkiea, Baud xxxii.), p. 135, taf. xxii. 18-20. 



Fig 



— Length of 

 areola 1 = 8 mm. 2 

 = 9 mm. 3 = 1 cm. 



