SPERMATOPHYTES 



187 



strobilus, are the megasporophylls (carpels). The whole structure is 

 like that of a huge flower (like a Magnolia), with perianth, stamens, 

 and conical mass of carpels. When the stamens are present, the ovules 

 are immature ; when the seeds are mature, the stamens have dis- 

 appeared, but their place of insertion is evident in the form of a 

 shoulder between the seeds and the enveloping bracts (fig. 429). 



FiG. 428. Diagram of strobilus of Cycadeoidea, showing the relation of parts 

 and a stamen unfolded. After WIELAND. 



Stamens. The stamens are like fern leaves that are twice pinnate 

 (fig. 428), and underneath the pinnules (sometimes twenty in number) 

 there are two lateral rows of synangia (fig. 43) > which are sori of the 

 Marattia type. The stamens are united below into a broad disk, becom- 

 ing free and pinnate above the ovule-bearing apex of the axis. The 

 synangia are almost identical in structure with those of Marattia, so 



