Heterospory

Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. Heterospory was evolved from isospory independently by several plant groups in the Devonian period cite journal|title=Heterospory - the most iterative key innovation in the evolutionary history of the plant kingdom|journal=Biological Reviews of the Cambridge Philosophical Society|date=1994|first=R.M.|last=Bateman|coauthors=W.A. Dimichele|volume=69|issue=|pages=315–417|id= |url=|format=|accessdate=2008-01-10 ] as part of the process of evolution of the timing of sex differentiation.IM Sussex (1966) The origin and development of heterospory in vascular plants. Chapter 9 in Trends in Plant morphogenesis, e. EG Cutter, Longmans.] Heterosporic plants produce small spores called microspores which either germinate to become male gametophytes or have reduced male gametophytes packaged within them, and similarly larger spores called megaspores that germinate into female gametophytes, or which have female gametophytes packaged within them.

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