288 MORPHOLOGY OF ANGIOSPERMS 



same time, the arguments in favor of the monophyletic origin 

 of Angiosperms are strong; and if this view be accepted, the 

 derivation of Monocotyledons from primitive Dicotyledons 

 seems to rest on stronger evidence than the reverse relationship. 

 It must also be said that the Gymnosperm origin of Angio- 

 sperms is not to be discredited so much now as formerly. 



The student of the phylogeny of any group of vascular 

 plants should be acquainted with certain general theoretical 

 views. Among them the origin of the sporophytic generation 

 is one of the most fundamental. Two theories are under dis- 

 cussion, known as that of homologous origin and that of anti- 

 thetic origin, names applied by Celakovsky. According to the 

 former theory, the sporophyte is the lineal descendant of the 

 sexless individuals common among Thallophytes and homolo- 

 gous with the sexual individuals; according to the latter the- 

 ory, the sporophyte is a new structure intercalated in the life 

 history of plants and holding no phylogenetic relation to any 

 preceding individuals. The theory of homologous origin is re- 

 ferred to Pringsheim in 1876 ; that of antithetic origin was 

 formulated by Celakovsky in 1877, but was presented in detail 

 by Bower in 1890. In 1896 the theory of homologous origin 

 was again brought into prominent notice by Scott in a presi- 

 dential address before the British Association ; and two years 

 later Bower, upon a similar occasion, defended the theory of 

 antithetic origin. A general presentation of the subject by 

 Klebs, 4 Lang, 5 and Hartog 6 followed, including the testimony 

 of recent investigations. Undoubtedly the strongest argument 

 in favor of the homologous origin of the sporophyte is derived 

 from the phenomena of apogamy and apospory; and among 

 Ferns these have been coming to light so rapidly and are in- 

 duced so readily that the powers of gametophyte and sporo- 

 phyte, at least in this group, seem to be easily interchangeable, 

 a fact most easily explained by their homologous character. It 

 will be noted that in all this discussion there is no suggestion 

 that sporophytes may have arisen in both of these ways, a possi- 

 bility that will be considered a little later. 



One of the most suggestive, theories of recent years is 

 Bower's l theory of the strobilus. ^sTo better statement of its 

 main points can be made than that of the author himself in 

 his summary. 



