XXXV] PACHYTESTA 323 



the seeds referred by Dr P. Bertrand 1 to Hexapterospermum may 

 appropriately be included in the genus Hexagonocarpus. 



Polypterospermum. Brongniart. 



This generic name was proposed for an ovoid seed from St 

 Etienne described as Polypterospermum Renaulti 2 ", hexagonal in 

 section with six deep and sharp flanges at the angles alternating 

 with six secondary ridges distinguished by their blunter edges 

 and slightly smaller depth (fig. 495, A). Without further ana- 

 tomical details it is hardly possible to say whether or not the 

 species represents a well-defined generic type, but it is not 

 improbable that a fuller knowledge would confirm Brongniart's 

 institution of a new generic designation. The seeds described 

 by Arber 3 and Kidston 4 respectively as Radiospermum ornatum 

 and Polypterospermum ornatum are transferred to Polygonocarpus 

 on the ground that they afford no evidence of anatomical characters 

 of the Polypterospermum type. 



Pachytesta. Brongniart. 



Brongniart 5 established this genus for some unusually large 

 seeds (fig. 496, A) from the Coal Measures of France reaching a 

 length of 11 12 cm. and resembling in form and size a hen's 

 egg. Petrified examples have been described by Brongniart and 

 Renault 6 , and Oliver 7 has given a lucid statement of the more 

 interesting features of this Permo-Carboniferous genus. 



Pachytesta gigantea (Grand'Eury). 



In the separation of nucellus and integument Pachytesta agrees 

 with Stephanospermum and Trigonocarpus. There is a double series 

 of vascular bundles in the outer part of the testa or exotesta (fig. 

 497,, ex) consisting of a spongy tissue bounded externally and in- 

 ternally by sclerotic layers : the exotesta is succeeded by a broader 

 endotesta of spongy consistency which Renault suggested may have 



P. Bertrand (13) PL VIT. 



Brongniart (74) p. 255, PI. xxm. figs. 13; (81) p. 27, PI. C, figs. 13. 



Arber, E. A. N. (14) p. 102, PL vn. figs. 3841. 



Kidston (14) p. 158, PL x. figs. 6, 7; PL xiv. figs. 59. 



Brongniart (74) p. 249, PL xxn. figs. 4, 5; (81) Pis. xvn. xxi. 



Renault (96) A. p. 389, Pis. 83, 84. 



Oliver (02). 



21 2 



