84 EMBRYOGENESIS IN PLANTS 



lends support to the view that the Ricciaceae are derivatively simple 

 organisms, and that their feebly developed chlorophyll is a remnant of 

 that which is present in forms with more elaborate sporophytes. 

 Furthermore, he has argued that since self-nutrition by photosynthesis 

 'was apparently a primary attribute of all sporophytes both in the 

 algae and land plants,' his observations are in accord with a homologous 

 theory of alternation of generations as the basis for the evolution of 

 land plants, rather than with the antithetic theory as advocated by 

 Bower. Bold (1940) has also suggested that the scarcity and inactivity 

 of the chlorophyll in the sporophytes of bryophytes may be a result of 

 the retention of the sporophyte within the gametophyte : and, similarly 

 the intrasporic development of the gametophytes in many heterosporous 

 pteridophytes and seed plants may have been a factor in their loss of 

 chlorophyll. Support for his views may perhaps be seen in the experi- 

 mental investigations of Studhalter (1938) in which he showed that 

 young excised sporophytes of Sphaerocarpus and Riella, cultivated in 

 water, reached full maturity through their own photosynthetic activity. 

 However, it is evident that during the early embryogeny of all bryo- 

 phytes, the sporophyte is completely dependent on the gametophyte 

 for its nutrition. 



Evans (1939) considers that the Anthocerotales also exemplify a 

 phylogenetically descending series, the relatively simple sporophyte of 

 Notothylas, as compared with the considerably more complex one of 

 Anthoceros, being due to reduction; i.e. Notothylas is the most 

 advanced genus in this group. 



