420 
STRUCTURE AND LIFE HISTORIES 
that the ovuliferous scale represents two sporophylls 
fused together. 
372. Megasporangia. As in Cycas, the megaspor- 
angium is an ovule, comprising a nucellus (sporangium 
proper), surrounded by an integument. At the apex the 
integument does not come quite together, so that a 
FIG. 310. Median longitudinal section of a pine cone, o.s, ovuliferous 
scale; ov, ovule at the base of a scale. 
tiny opening or pore (the micropyle) is left. The micropyle 
leads to the pollen-chamber below (Figs. 309 and 311). 
The megaspores are more backward in development than 
the microspores, the spore-mother-cell not appearing until 
June. Reduction by two divisions gives rise to either 
three or four megaspores in a row, but only the basal one 
ever germinates; the others become disorganized and 
furnish nourishment for the one that germinates. 
