394 



BENNETTITALES 



[CH. 



distally as a slender cylindrical column or micropylar tube at 

 the base of which it becomes broader owing to the increase in 

 breadth of the middle or palisade layer. A nucellar beak projects 

 as a cone into the base of the micro- 

 pylar tube. No pollen-chamber has 

 been found. It is noteworthy that 

 the micropyle is closed in the ripe 

 seeds. Internal to the testa there 

 is a crushed membrane separated 

 from the embryo by a space (fig. 

 521, D, sp] : this is the remains of 

 the nucellus and, as Solms-Laubach 

 points out, there is no proof that 

 any endosperm was present in 

 the ripe seeds 1 . The embryo con- 

 sists of a short axis, the conical 

 radicle and the very short apex of 

 the epicotyl, also two equal coty- 

 ledons each with a few vascular 

 bundles (fig. 521, D). The long 

 interseminal scales, as seen in 

 transverse section in the lower part 

 of a flower between the sporophylls, 

 appear as compressed polygonal 



organs (fig. 521, B, i) with an axial vascular strand surrounded 

 by parenchyma and limited by a strong epidermis ; they pass up 

 between the seed-stalks, m, and in the distal end become con- 

 siderably enlarged (figs. 514, 515), gradually expanding to form 

 a truncate or slightly pyramidal apex (figs. 553, 563). The 

 swollen peltate apices of adjacent scales form a continuous covering 

 to the flower interrupted, except in the lower sterile part of the 

 flower, by symmetrically disposed cylindrical micropylar tubes 

 (fig. 515). The peripheral interseminal scales form a homogeneous 

 parenchymatous tissue which springs from below the edge of the 

 receptacle (fig. 521, A, B, pr) and the individuality of the scales 

 composing this ' pericarp ' is indicated by occasional invaginations 



1 It is possible that, as Scott suggests, a small patch of endosperm is repre- 

 sented in a seed of this species figured by him. Scott (09) B. p. 569, fig. 203, D, e. 



FIG. 523. Cycadeoidea Gibsoniana. 

 Seed with embryo. (British 

 Museum, 41388.) 



