Portuguese
megásporo Spanish
macróspora 
A type of spore that is present in heterosporous plants; large spore, germinates into a female gametophyte, which produces egg cells.
1
The nucellus is a cellular tissue enveloping one large cell, the embryo-sac or macrospore.
2
But the formation of the macrospore or embryo-sac is simpler than the corresponding process in cryptogams.
1
The megaspore mother cells develop just after pollination in early May and mature in mid-late June.