XLl] DESMIOPHYLLTJM . 71 



leaves that in the absence of evidence as to the habit of the shoots 

 cannot be assigned to more precisely defined genera such as 

 Phoenicopsis or Podozamites. Nathorst^ employs D.esmiophyllum 

 for some Phoemcopsis-like leaves from Jurassic rocks in the New- 

 Siberian Islands which may be specifically identical with those 

 described by Graf Solms from Franz Josef Land, which I propose 

 to call Desmiophyllum Solmsi. In view of the probability that 

 these leaves belong to a species of Phoenicopsis, a brief description 

 of their structure may be conveniently inserted here. 



Desmiophyllum Solmsi sp. nov. 



The collection of plants obtained by the Jackson-Harmsworth 

 Expedition (1894 — 96) to Franz Josef Land includes several 

 specimens of matted linear leaves some of which are figured by 

 Newton and TealP. Similar leaves collected by Nansen are 

 described by Nathorst*. Subsequently Solms investigated the 

 structure of the leaves figured by Newton and Teall and the 

 photographs reproduced in fig. 662 were taken from sections of 

 the silicified material in the Museum of the Geological Survey. 

 The largest specimens reach a length of 10 cm. and are 5 — 10 mm. 

 broad ; the veins are unbranched and there are six in a breadth of 

 3 mm. of lamina. In transverse section the lamina is of fairly 

 uniform breadth or, owing to the partial coUapse of the intercostal 

 mesophyll, it is characterised by prominent ribs (fig. 662, A). 

 The vascular bundles are collateral, enclosed in a sheath of rather 

 thick- walled cells : the xylem elements are spiral and scalariform 

 and, as Solms states, the occasional preservation of single row^s of 

 circular bordered pits and the occurrence of lateral sieve-plates 

 point to a Gymnospermous affinity. The mesophyll is fairly 

 homogeneous and lacunar as shown in fig. 662, A and B : in the 

 tangential section (B) the lacunar mesophyll is seen between the 

 veins and their associated rows of rectangular cells. . The epidermal 

 cells are thickly cuticularised and papillose. In one section a few 

 stomata were found showing two dark guard-cells, 40 fj. long, 

 surrounded by six faintly outhned cells (fig. 662, C) agreeing with 

 those of Ginkgo and Ginkgoites, except in the absence of any 

 overarching papillate subsidiary cells. This may, however, be 



1 Nathorst (07) p. 4. 



2 Newton and Teall (97) ; (98). ' Nathorst (99). 



