THE EVOLUTION OF PLANTS 



2IQ 



sexual in effect a microsporophyll or a megasporophyll, 

 from which complex forms were derived by elaboration. 

 This latter view, however, is not in harmony with avail- 

 able evidence from fossil plants, such as that afforded by 

 Cycadeoidea. 



"The strobiloid theory of the flower seems in the present 

 state of our knowledge to stand alone as a working hy- 



ABC 

 FIG. 103. Theoretical stages in the reduction (from Cycadeoidea to 

 modern Angiosperms) of staminate discs represented as segments. A, 

 any common campanulate form with simple stamens (e.g., morning 

 glory); B, hypothetical Cycadeoid reduced to a single synangium to each 

 frond component; C, inner view of a sector of a Williamsonia mexicana 

 disc; D, sector of a Cycadeoidea dacotensis disc with the pair of shoulder 

 spurs borne by each frond. (After Wieland.) 



pothesis. If we reject it, we are left without any historical 

 clue to the origin of the floral structure of Angiosperms. 

 If we accept it, the Primitive Angiosperm must be cred- 

 ited with a flower resembling that of Magnolia or Lirio- 

 dendron in general plan." 1 From this it follows that the 

 Magnoliacea must be among the most primitive, if not the 

 most primitive, of all Angiosperms, as Wieland first and 

 Hallier later and independently pointed out. 



1 Sargant, Ethel. The reconstruction of a race of primitive Angiosperms. 

 Ann. Bot. 22:121-186. April, 1908. 



