CYCADOFILICALES 



21 



surrounds not a naked seed, but an ovary. A diagram of the seed 

 described as Lagenostoma lomaxii (fig. i8) shows the general struc- 

 ture of the seeds of Lyginopteris. The nucellus is free only at the tip 

 and, at maturity, has a central core surrounded by a bell-shaped 

 crevice, the pollen chamber. The outer part of the ovule, shown in 

 black in fig. i8 is hardened, like the stony layer of a cycad seed; 

 within the hardened portion is a fleshy layer, with the inner set of 

 bundles. Another set of bundles, 

 more numerous than those of the 

 inner set, supplies the cupule. If the 

 cupule were closely applied to the 

 ovule, as it probably was in the 

 early stage of development, a longi- 

 tudinal section would look somewhat 

 like that of a cycad seed, with a vas- 

 cular system on each side of the stony 

 layer. A detail of the top of the 

 ovule, with microspores in the pollen 

 chamber, is shown in fig. 19. An 

 earlier stage, drawn from the same 

 section from which the photomicrograph, fig 

 shown in fig. 20. 



The embryo. — While some of the seeds show traces of the female 

 gametophyte and even enough of the archegonia to show that they 

 are of the elongated type, no embryo of any of the Cycadofilicales 

 has ever been discovered. Where mature seeds, in organic connec- 

 tion with foliage leaves, have been discovered, only impressions have 

 been available. Isolated seeds, which dropped off and got into suit- 

 able places for preservation, were probably abortive and never would 

 reach the embryo stage. 



Other Cycadofilicales. — While Lyginopteris is the most com- 

 pletely known of any of the Carboniferous plants, there has been a 

 partial assembling in many others; in fact, there has been so much 

 assembling that an unattached fernlike leaf, in the vegetative condi- 

 tion, is more likely to belong to the CycadofiUcales rather than to the 

 true ferns, just as in the angiosperms double fertilization is so preva- 

 lent that one now assumes it to occur unless there is good proof to 

 the contrary. 



Fig. 17. — Lyginopteris lomaxii: 

 seed surrounded by a glandular cu- 

 pule. — From a restoration by Oliver 

 and ScoTT.«i 



16, was made, is 



