The Collaborative International Dictionary of English v.0.48:
Macrospore \Mac"ro*spore\, n. [Macro- + spore.] (Bot.) One of the specially large spores of certain flowerless plants, as Selaginella, etc. [1913 Webster]WordNet (r) 3.0 (2006):
macrospore n 1: larger of the two types of spore produced in heterosporous plants; develops in ovule into a female gametophyte [syn: megaspore, macrospore]