SPERMATOPHYTA 



313 



Fig. 260. Cross section of small stem of Lyuiiiopteris oldhamia, X 5; a, sclerenchyma bands 

 in outer cortex; h, inner cortex and phloem; c, double leaf trace; d, secondary xylem; 

 e, primary xylem;/, pith. (From Arnold.) 



B C 



Fig. 261. Microsporangia of Cycadofilicales. A, diagrammatic longitudinal section of a 

 fertile pinnule of Crossotheca, showing epaulet type with peltate limb and pendent sporangia, 

 X3; B, cross section of same, showing bilocular sporangia; C, cupule type, Codonotheca, 

 with sporangia on the inner surface of the valves, natural size. (A and B, after Kidston; 

 C, after Sellards.) 



which the microspores accumulated. The Cycadofilicales must have had 

 swimming sperms. 



Gametophytes. Pollen grains, found in pollen chambers, contain a 

 tissue of numerous cells, all of which wei-e probably spermatogenous. 

 The sperms seem to agree in form with those of existing cycads. No 

 evidence of pollen tubes has ever been found and it is probable that they 



