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Life cycle of a fern (genus Polypodium). The sporophyte generation is photosynthetic and is independent of the gametophyte. The sporangia are protected by a layer of cells called the indusium. This entire structure is called a sorus. Meiosis within the sporangia yields a haploid spore. Each spore divides mitotically to produce a heart-shaped gametophyte, which differentiates both archegonia and antheridia on one individual. The gametophyte is photosynthetic and independent, although it is smaller than the sporophyte. Fertilization takes place when water is available for sperm to swim to the archegonia and fertilize the eggs. The sporophyte has vascular tissue and roots; the gametophyte does not.

(A) Hyphae of the blastocladia-lean fungus, Allomyces sp. Note a terminal zoosporangium (ZS) containing zoospores. The spiny, dark, thick-walled resting spores (RS) within the hyphae are those of a zoosporic fungal parasite, Rozella allomycis, of uncertain taxonomic placement. Bar = 10 μm. (B) Lobosporangium transversale. The zygosporic fungus in the Mortierellales has unusual spiny lobed sporangia (Benny and Blackwell, 2004). Bar = 50 μm. (C) Sarcoscypha coccinea. The several cm diameter fruiting body of the scarlet cup ascomycete, Sarcoscypha coccinea. Ascospores are formed within asci on the inner surface of the cup. (D) Mutinus sp. A stinkhorn similar to one mentioned in the text that caused a search for a dead body (Anonymous, 2005). Stinkhorns produce noxious compounds that attract insect spore dispersers. The dark slimy mass of spores has been partially removed by flies.
SOURCES: (A) photo courtesy of Timothy Y. James, provided by Meredith Blackwell (2009). (B) micrograph courtesy of Kerry O’Donnell, provided by Meredith Blackwell (2004). (C) photo courtesy of eriotropus/coqui, provided by Meredith Blackwell (2002). (D) photo courtesy of Nhu H. Nguyen, provided by Meredith Blackwell (2005).