THE EVOLUTION OF PLANTS 



607 



features that characterize the Cycadofilicales, their 



development of a bisporangiate strobilus with two set 



of sporophylls, related to one an- 



other as they are in the flower of 



the Angiosperms. indicates a gen- 



etic relationship to that group, as 



does also the fact that the seeds, 



enclosed in a fruit, possess a dicot- 



yledonous embryo, without endo- 



sperm. In other features the Ben- 



nettitales are unlike the Angio- 



sperms; the ovules, for example, 



are enclosed by sterile scales, in- 



stead of by the carpels on which 



they are borne, and the protrusion 



of the pollen-chamber through the 



micropyle signifies the gymno- 



spermous type of fertilization. 



These and other comparisons in- 

 dicate that the Bennetti tales were 

 essentially Gymnosperms having 

 certain Angiospermous characters, 

 and therefore, while they are not 



to be considered as the ancestors 



P . * A ... -LIT Flower with perianth re- 



of the Angiosperms, it is probable moved> showing the com- 



that they and the modern dicoty- pound pistil, and four of the 



J stamens. Most of the sta- 

 ledons are both descended from a mens have been removed. 



common branch of the ancestral 



429. Magnolia 



tree. Among modern plants, the at the points of attachment. 

 flower of the magnolias most 



closely resembles that of Cycadeoidea in the spiral arrange- 

 ment of its stamens and pistils (Figs. 428 and 429.). How 



