128 



HEREDITY AND EVOLUTION IN PLANTS 



monocotyledony seems the simpler, more primitive condi- 

 tion, it is really a later phenomenon, the monocotyledons 

 being derived from the dicotyledons by simplification.^ 



As a further example there may be cited the application 

 of the method of comparative anatomy to solve the problem 



Fig. 65. — Progressive sterilization of tissue in sporophytes. a, Riccia 

 trickocarpa (mature) ; b, Marchantia polymorpha (embryo) ; c, Marchantia 

 (mature); d, Porrella, a leafy liverwort (mature); e, anthoceros; /, Lyca- 

 podium Selago; g, Lycopodium complanatum; h, Botrychium Lunaria 

 (Eusporangiate); i, Polypodium venosum (Leptosporangiate). (Re- 

 drawn from various sources.) 



of the origin of the leafy sporophyte. As noted above 

 (If loi) , the most primitive spore-producing phases (sporo- 

 phytes) of the lower liverworts (Hepaticas) consist 

 almost entirely of "fertile" {i.e., reproductive) cells, 

 and the relative amount of vegetative or sterile tissue 

 1 Seepage 223. 



