358 MISCELLANEOUS SEEDS [CH. 



flanges project slightly beyond the apex of the seed and there is 

 a small notch at the base ; the nucule is 5 cm. long and 1 cm. 

 broad. While it is not improbable that this seed is generically 

 identical with Brongniart's Tripterospermum 1 , it is safer, in the 

 absence of structural details, to employ the less committal term. 

 There is no information with regard to the nature of the parent- 

 plants of species of Polypterocarpus. The English seed from the 

 Middle Coal Measures of Derbyshire and the Staffordshire coal- 

 field described by Arber 2 as Radiospermum ornatum and by 

 Kidston 3 as Polypterospermum ornatum affords another example 

 of Polypterocarpus as the generic name is here employed. 



Rhynehogonium. Heer. 



Heer 4 proposed this generic name for some globose, ovate, 

 or oblong ' fruits ' from Lower Carboniferous strata in Spitzbergen, 

 including also fragments of 'leaves' which without satisfactory 

 evidence he believed to belong to the same plant. The supposed 

 fruits are clearly seeds, and Nathorst regards the 'leaves' as 

 portions of a Fern rachis. Heer described four species, but these 

 have since been reduced to two, and indeed it is probable that 

 only one type, Rhynehogonium costatum, is represented. Nathorst 5 

 compares Heer's seeds with a Lower Carboniferous species described 

 by Young 6 as Trigonocarpum gloagianum, the resemblance of which 

 to the Spitzbergen seeds was pointed out by Kidston. A seed 

 of Rhynehogonium costatum is about the size of a hazel-nut and 

 may reach a length of 21 mm. ; it is ovate, with a broad rounded 

 base, and in the upper third is tapered and conical, the sides of 

 the characteristic snout being distinguished from the smooth 

 surface of the rest of the seed by the presence of eight ribs con- 

 verging towards the apex (506, G). Zalessky 7 recorded closely 

 allied seeds from Lower Carboniferous beds in Northern Russia, 

 assigning them to a new genus Boroviczia, the type-species being 

 B. Karpinskii] he adduced arguments in favour of Heer's inter- 

 pretation of the fossils as fruits but, according to Nathorst, this 

 view has been abandoned. In his recent memoir on the Culm 



1 See page 321. 



2 Arber, loc. cit. p. 102. 3 Kidston, loc. cit. p. 158. 



4 Heer (77) i. p. 19, PI. v. figs. 111. 6 Nathorst (94) A. p. 48, PL iv. figs. 7, 8. 

 Young (69) PL iv. figs. 9, 10; (76) p. 36. 7 Zalessky (05). 



