No. 438-] ORIGIN OF THE SPOROPHYTE. 419 



better discussed in a consideration of the evolution of the 

 sporophyte than under the title of the present paper. 



The origin of the sporophyte involves the examination of con- 

 ditions previous to the bryophytes, i. c, among the groups of the 

 algas and fungi (thallophytes) and we will now consider these. 



As is well known the algae and fungi present organisms far 

 more various in the succession of forms comprising their life 

 histories than the higher plants. There is no general rule of 

 development in this assemblage of diverse groups but rather a 

 number of habits presented by the divergent lines in relation to 

 their various modes of life. In this respect the thallophytes 

 stand in sharp contrast to all plants above the bryophytes. The 

 antithesis of sporophyte and gametophyte, if present at all, is 

 greatly obscured by the intercalation of many and various means 

 of asexual reproduction which may give an indefinite and very 

 irregular succession of individuals. For many years botanists 

 have attempted to define among these lower plants life histories 

 comparable to the alternation of gametophyte and sporophyte. 

 Some of these suggestions appear probable, others have been 

 completely disproved by experimental studies on development. 



The test of an alternation of generation involving a game- 

 tophyte and sporophyte must always lie with the activities of 

 the sexually formed spore. If this cell invariably produces a 

 phase different from its parent plant then we may properly 

 inquire whether such a structure does not have in itself potenti- 

 alities that separate it as a distinctly new form of development. 

 It may then be called a sporophyte in contrast to the gamete 

 bearing individual and the succession of generations will be 

 antithetic at this point in the life history. 



It does not matter how numerous are the successions of gen- 



