CRYPTOGAMS 



351 



bryophytes, and may be represented by the same formula. 

 The chief difference is in the relatively much greater im- 

 portance of the sporophyte, which may be expressed by 

 putting it first : — 



S—^o—^G<^ J>o6a—>S-^o^G<^ N oos—>S-^o—>G etc. 

 ^mg mg 



But some of the pteridophytes — of which the Selaginella 

 offers a conspicuous example — have differentiated their 



34 507 508 



;. — A kind of pteridophyte (Selaginella martensii) with its organs of 



(4, a fruiting branoh ; 505, a microsporophyll with a microsporan- 



icTospores through a rupture in tho wall ; 500, a mogasporophyll 



"anirium : 507. megasDores : 508, microspores. (From Coulter's 



Figs. 504-508. 



fructification: 504, ._ 



gium, showing microspores through a rupture in the wall; 50f 

 with a megasporangium ; 507, megaspores ; 508, microspores. 

 " Plant structures.") 



