XXIX] HETERANGIUM 81 



so-called cupule. The transverse section shown in fig. 414, B, 

 is taken at the level of the roof of the pollen-chamber and of 

 the nucellar cap ; it illustrates the contrast between the ' multi- 

 seriate annulus' and the central column of small parenchyma. 



Sphaerostoma differs from Lagenostoma in the whorl of crests 

 around the micropyle, in the nearly hemispherical form of the 

 lagenostome and in the relatively wider pollen-chamber with 

 its peculiar form of dehiscence. Miss Benson, while regarding 

 Sphaerostoma as similar to Lagenostoma in general plan, believes 

 the distinguishing features of the former to be such as are con- 

 sistent with a more primitive form. 



An important argument in support of connecting this seed 

 with Heterangium is derived from the juxtaposition of some 

 seeds and portions of Heterangium petioles, a juxtaposition that 

 is believed to demonstrate original continuity. 



Grand'Eury 1 has recorded the association of two species of 

 leaves, Sphenopteris elegans and S. dissecta, with small seeds 

 compared by him with Lagenostoma. In the absence of petrified 

 specimens it would be practically impossible to distinguish between. 

 Lagenostoma and Conostoma or Sphaerostoma. 



Carpentier 2 has described some impressions from French 

 Westphalian beds as Conostoma and he records cupules without 

 seeds on fronds of Sphenopteris obtusifolia which he speaks of as 

 having transverse striations like those of Heterangium. Dr Kidston 

 pointed out to me that the surface-features of the Sphenopteris 

 rachis are probably due to ramental scales and not to the presence 

 of horizontal sclerous bands. Carpentier's seeds may be compared 

 with Lagenospermum Sindairi. 



Heterangium tiliaeoides Williamson, Phil. Trans. R. Soc. Vol. 178, 



p. 289. 



This species, founded by Williamson on material from the 

 Lower Coal Measures of Halifax, Yorkshire, while agreeing in 

 the structure of the primary stele and in the general features 

 of the cortex with the older Heterangium Grievii, is clearly dis- 

 tinguished by certain well-marked characters. Sclerous groups 

 occur in the inner cortex as in H. Grievii but they are present also 



1 Grand'Eury (05 2 ). 2 Carpentier (11) PI. xn. fig. 1. 



S. m 6 



