584 



A TEXTBOOK OF THEORETICAL BOTANY 



passed through an early stage to which Selaginella yields the clue. In fact 



the plant provides us with a link between the two great groups, Cryptogams ^L 



and Phanerogams, which helps us to understand how they are related. 'f 



1- .^J 



Sporophyll 



Ligule 



Microsporangium 

 Sporangiophore 



Megasporangium 



Fig. 593. — Selaginella kraussiana. Longitudinal section 

 of the strobilus showing the arrangement of the 

 megasporangia and microsporangia. 



The Male Gametophyte 



In Lycopodium the prothallus is reduced to a saprophytic underground 

 structure, but in Selaginella the reduction of the gametophyte generation has 

 gone further, as the prothalli do not even emerge from the spores. Both 



