XXXV] CLASSiriCATION OP SEEDS 307 



recently brought forward by Nathorst^ renders probable a con- 

 nexion of a presumably radiospermic seed Lagenos-permum Arheri^ 

 with the Lower Carboniferous fronds Adiantites bellidulus Heer, 

 and this furnishes an interesting illustration of the association of 

 both platyspermic and radiospermic seeds with the same generic 

 type of fohage. While retaining Radiosperm and Platysperm as 

 convenient descriptive terms, I have not adopted them as group- 

 designations on the ground that they do not in themselves serve 

 as trustworthy criteria of relationship. Attention is called by 

 Sahsbury* to the occurrence of bilaterally and radially symmetrical 

 fruits among British Carices and to a similar mixture in the family 

 Polygonaceae. 



The acquisition of more detailed and accurate knowledge of 

 Palaeozoic seeds led to an extension of the two-fold division of 

 Brongniart and Ohver which is based on such characters as the 

 position of the vascular tissue in relation to the integument and 

 nucellus, the form of the pollen-chamber, and other features. 

 The division Lagenostomales has been instituted for Lagenostoma 

 and some other Radiosperms connected by certain important 

 characters: these seeds may be referred to the Pteridospermeae 

 though it is only in the case of Lagenostoma, and to a less extent 

 Sphaerostoma, that a correlation between vegetative organs and 

 seeds has been rendered sufficiently probable to justify an assump- 

 tion of generic identity. The name Trigonocarpeae* has recently 

 been used for a section of Radiosperms represented by Trigono- 

 carpus, Stephanospermum, and other genera. Although the genus 

 StepJianospermum, as OUver^ says, may be regarded as the type- 

 genus of a group of seeds, it is more fitting, as the same 

 author^ insists, to adopt a divisional term based on the generic 

 name of the much more widely spread and more famihar Trigono- 

 carpus. For the sake of uniformity in nomenclature it is proposed 

 to adopt the name Trigonocarpales instead of Trigonocarpeae to 

 rank with Lagenostomales. 



The Platyspermeae comprise such seeds as Cardiocarpus, 

 Mitrospermum, and Rhabdospermum, genera characterised by 



' Nathorst (14) p. 32. ^ See page 173. 



» Salisbury (14) p. 71. ' Salisbury (14). 



s OUver (04) B. p. 392. « OUver (07). 



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