megaspore noun. ['mɛgǝspɔ:] M19.
[from MEGA- + SPORE.]
Botany. The larger of the two kinds of spores in heterosporous cryptogams, which develop into female gametophytes; the analogous structure (the immature embryo sac) in seed plants.

■ megaspo'rangium noun, pl. -gia, a sporangium containing megaspores L19.

■ mega'sporophyll noun a leaf or modified leaf which bears megasporangia E20.

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