446 SELAGINELLA i ..... xwii 



more ovaiR's [tny) are formed on it, each consisting of a 

 short neck, an ovum, and two canal-cells afterwards con- 

 verted into mucilage : there is no venter, and the neck con 

 sists of only two tiers of cells. 



The oosperm divides by a plane at right angles to the 

 neck of the ovary, forming the earliest or two-celled stage of 

 the polyplast. The upper cell undergoes further division, 

 forming an elongated structure, the suspensor {spsr) : the 

 lower or embryo proper {etnl>) is forced downwards into the 

 secondary prothallus by the elongation of the suspensor, 

 and soon passes into the phyllula stage by the differentiation 

 of a stem-rudiment {st), two cotyledons (r/), a foot (/), and 

 subsequently of a root. 



A further reduction of the gamobium is seen in Selagi- 

 nella : both male and female prothalli are quite vestigial, 

 never emerging from the spores : and the spermary and 

 ovary are greatly simplified in structure. 



