CYCADOFILICALES 



23 



and an outer layer with layers of thin-walled and thick-walled cells 

 alternating with each other, as in Lyginopleris. 



Fig. 19. — Lyginopleris lomaxii: longitudinal section of upper part of seed; 0, micro- 

 pyle; i, integument; n, central core of nucellus and n', outer part of nucellus with the 

 pollen chamber (p) between; g, pollen grains; n", part of nucellus; m, thick megaspore 

 membrane; about Xso. — After Oliver and Scott.«' 



Fig. 20. — Lyginopleris ovoides: upper part of the seed shown in lig. 16; n, inner part 

 of nucellus; 0, hard outer part of nucellus; p, pollen chamber; m, megaspore membrane; 

 X36. Drawn from a slide in the paleobotanical collection of the University of Chicago. 

 — From Coulter and Chamberlain's Morphology of Gymnosperms (University of Chi- 

 cago Press). 



Spherostoma is probably the seed of Heterangium, but no organic 

 connection has yet been discovered. The seed is small, about 3.5 mm. 



