XLVIl] FRENELOPSIS 343 



Thuiles Hoheneggeri on the ground that the external features of 

 the vegetative shoots indicate an affinity to the recent genus 

 Frenela (= Callitris) rather than to Thuya or Cupressus. The 

 resemblance to Callitris was recognised by Ettingshausen. The 

 most striking features of Frenelopsis are the comparatively long 

 internodes of the jointed stems and branches (fig. 763, A), the 

 occurrence of appressed leaves in opposite pairs or four in a verticil, 

 concrescent with the whole intei nodal surface and projecting 

 slightly above each nodal line as small broadly triangular scales, 

 the presence of longitudinal lines of small dots on the internodal 

 regions due to rows of stomata characterised by 4 5 accessory 

 cells surrounding the depressed guard-cells 1 (fig. 763, D, E). The 

 smaller branches closely resemble those of species of Cupressineae 

 (fig. 763, C) or Callitrineae in leaf-form and branching, but older 

 branches from which the leaves have partially or wholly disappeared 

 often differ considerably from the younger foliage-shoots and by 

 themselves afford little or no indication of their true nature. 

 Further details are given in the description of representative species. 

 Frenelopsis is characteristic of Wealden or higher horizons in 

 the Lower Cretaceous series; it occurs in Silesia, Bohemia, Portugal 

 and the South of France and in some North American localities, 

 particularly in the Potomac formation. Heer 2 records the species 

 from Lower Cretaceous rocks in West Greenland but some of the 

 original specimens which I had an opportunity of examining in the 

 Stockholm Museum afforded no satisfactory evidence of their 

 systematic position. Though assigned by Heer to the Gnetales, 

 Frenelopsis is usually regarded as a Conifer agreeing with Callitris 

 more closely than with any other existing genus. In their descrip- 

 tion of some fossil .shoots referred by Newberry 3 to Frenelopsis 

 gracilis Hollick and Jeffrey 4 , who institute a new genus Raritania 

 for this species, state that they have reason to believe that some 

 American specimens correctly assigned to Frenelopsis are examples 

 of Gnetalean plants. Nothing is known of any reproductive organs, 

 but such information as we have with regard to the habit of the 

 vegetative shoots and the structure of the stomata would seem to 



1 Zeiller (82) A. p. 231, PI. xi.; Thompson (12 3 ) PI. v. 



2 Heer (75) ii. p. 73, PL xvra. figs. 58; (82) i. p. 7,. PL n. figs. 13. 



3 Newberry and Hollick (95) p. 59, PL xra. figs. 13. 



4 Hollick and Jeffrey (09) B. p. 26. . 



