Source : Webster's Revised Unabridged Dictionary (1913)

Macrospore \Mac"ro*spore\, n. [Macro- + spore.] (Bot.)
   One of the specially large spores of certain flowerless
   plants, as {Selaginella}, etc.

Source : WordNet®

macrospore
     n : larger of the two types of spore produced in heterosporous
         plants; develops in ovule into a female gametophyte [syn:
          {megaspore}]