SPERMATOLMIVTIlS 



20^ 



bears one or two Ijractlcls and a terminal o\aik' (llg. 463). The bearing 

 of o\-ules on seeondary axes of the strofiilus results in what is ealled a 

 compound slrobiliis,ii ty])e of strobilus eharactcristie of certain conifers. 



Ovules. — Although the 

 structure of the testa is not 

 clear in the sections that have 

 been made (fig. 463), two 

 layers are evident (the outer 

 fleshy and the stony), and it 

 is probable that an inner 

 fleshy layer was also present. 

 This t}'jje of testa is char- 

 acteristic of the whole cycad 

 line of gymnosperms. An- 

 other primitive feature of the 

 ovule is that the nucellus is 

 quite free from the integu- 

 ment, and that one of the 

 sets of vascular strands trav- 

 erses the outer fleshy layer, 

 ajid the other set tra\'erses 

 the peri]")heral region of the 

 nucellus. This structure is 

 duplicated only among the 

 Cycadofilicales. There is also 

 a [jrominent nucellar beak 

 and a large pollen chamber, a 

 structure which indicates the 

 existence of swimming sperms. 



Male gametophyte. — The 

 pollen grains are preserved in 

 abundance, and in fa\'orable 

 s]iecimens a group of internal 

 cells is evident (fig. 464), 

 vhich must represent a male gametophyte; l)ut whether these cells are 

 vegetative or spermatogenous or both cannot be determined. In either 

 case, the number of cells indicates a very primitive condition. 



Female gametophyte. — The female gametophytes resemble those of 

 modern gymnosj)erms. Two archegonia ha\'e been seen, and between 



Fig. 462. — SfCtion of staniinate strobilus of 

 one of till-' Cordaitales, sliowing tlie spirally ar- 

 rant^cd sterilo bracts, and the stalked stamens 

 bearing tcritiinal sjjorangia (the longitudinal de- 

 hiscence of the sporangia not shown). — Alter 



P EN.^ULT. 



