Further Notes on Seed Struchires. 



141 



Of the several species B. Morierei has distinctly the heaviest 

 walls, B. Oibsonianus walls of intermediate thickness, and 

 some of the American seeds the thinnest walls of all, though 

 there is essential agreement in testal structure extending to the 

 cell types of the three component layers. 



To show this structural similarity and to further bring out 

 minor details proving that in Cycadeoidea we deal with a 



S.736X50. 



A.— Cycadeoidea turrita (?). Tangential section through the selerotesta. 

 x 88. The hasal walls of these cells are far thicker than the lateral and 

 tangential walls ; the cell interior varies much in appearance, or only the 

 solid base may appear. Again, the outer face may show a marked central 

 concavity. 



B. — Bennettites Morierei (Sap. et Mar.) type. x 88. Longitudinal section 

 of testa traversing valley below the shoulder where ribs first become prom- 

 inent. Compare with fig. 2D. 



C— Cycadeoidea Wielandi. S. 736. T. 393. x 50. Longitudinal section 

 of micropylar tube in seed type without distinctly developed "blow off." 

 Palisaded wall in continuation from middle stone. Interior space filled with 

 soft squarish cells, in bulk producing somewhat cancellated appearance. 

 Dotted line shows limit of exterior surface, the thin outer layer failing of 

 conservation. 



genus of world-wide distribution and long persistence in time, 

 I have made the series of camera lucida drawings shown in 



inner flesh would favor rupture of the nucellar sack with more or less dis- 

 persionxof such rounded cells, but this explanation is tentative. 



The close agreement of the two European species and the American forms 

 retaining the "blow off" layer is noteworthy, while the two seeds of Ben- 

 nettites showing difference in the indurated layer, as seen in about the 

 same region of the testa, suggest the character of longitudinal fluting, and 

 completely bridge the slight structural gap between the commoner American 

 form C, and Bennettites Morierei, no more than mere specific differences 

 appearing. 



