IV] THE FLOWER AND METAMORPHOSIS 53 



these were all alike, as were also the sporangia 

 which contained them. Such a condition is still seen 

 in the Ferns, Club-Mosses, and Horsetails of the 

 present day. It is held that sporangia essentially 

 similar to theirs were modified in the course of 

 descent, in accordance with the differentiation of sex, 



Fig. 10. Median section of the flower of a Butteicui^, showing its 

 constituent parts. On the outside (lowest down in the drawing 

 and shaded) are the sepals of the calyx: within this the large 

 petals of the corolla of which three are shown : within this and 

 seated higher on the axis are the numerous club-shaped stamens, 

 each of which bears four pollen-sacs. Centrally in the flow^er are 

 the numerous carpels, one of which is dissected so as to show its 

 single ovule, or future seed. (From Le Maout and Decaisne.) 



until they finally assumed those two apparently 

 different forms, the pollen-sac and the ovule. It is im- 

 portant for our enquiry into the relation of the flower 

 and the foliage-shoot that this correspondence of the 

 ovule and the pollen-sac with the sporangia of Ferns 

 and Club-Mosses should be realised. Its acceptance 



