Heterosporous Plants

... Heterosporous Plants ('hetero-' = 'different') An important change took place in many of the major plant groups during the Devonian period. Until this period, each sporophyte plant had produced spores of one kind: homospores. Now, some plants began to produce two kinds of spores from two kinds of sporangia, an evolutionary stage which some algae were also to reach in the sea. These plants were said to be heterosporous. In heterosporous plants the two different spores germinate into two small, but distinctly different, gametophytes which remain within spores and never grow into a large green plant. The two kinds of spores are different in size, for specific reasons. The larger type (megaspores) becomes a female gametophyte with female sex organs. It therefore contains the food reserves necessary for the early growth of the future plant. The smaller spores (microspores) which become the male gametophytes have no food reserves as their sole function is

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