SPERMATOPHYTES 
I8 7 
strobilus, are :ne 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). 
FlG. 428. Diagram of strobilus of Cycadcoidea, 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. 430), 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 
