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A spore is a unit of sexual or asexual reproduction that has been modified for dispersion and survival in difficult settings for long periods of time.

Homosporous: a plant that only produces one type of spore.

Heterosporous plants produce two types of spores, primarily Macrospore and Microspore.

Lower vascular plants, such as ferns and club mosses, are primarily homosporous (produce only one type of spore).

The majority of pteridophytes are homosporous, however, some are heterosporous.

The majority of gymnosperms are heterosporous, with a few homosporous.

All spermatophytes, or seed plants, are heterosporous. Megaspores (female) and microspores (male) are the two types of spores they produce (male).

Microspores germinate into male gametophytes, whilst macrospores germinate into female gametophytes. Pteridophytes are midway between bryophytes and gymnosperms in plant evolution. Gymnosperms are heterosporous, while bryophytes are homosporous. Because sexual dimorphism leads to cross-fertilization, this state has progressed.