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Lycophytes - Lycopodiidae, Selaginelidae, Isoetidae

haploid plants chromosomes class

Lycophytes are vascular plants in the class Lycopodiopsida, a division of vascular plants known as Pteridophytes (the ferns and their allies). The class Lycopodiopsida is divided into three subclasses: the Lycopodiidae, Selaginellidae, and Isoetidae.

Like other pteridophytes, the lycophytes have an alternation of generations, consisting of two generations of morphologically different plants. The larger, longer-lived generation is diploid (having both sets of chromosomes) and known as the sporophyte stage. This stage produces structures known as sporangia. The sporangia produce haploid spores (having one set of chromosomes) that can be aerially disseminated into the environment. If a spore lands on a suitable, moist substrate, it will germinate and grow into an independent, haploid structure known as a prothallus (or gametophyte). The prothallus is typically about 0.08-0.12 in (2-3 mm), long and contains both male (antheridia) and female (archegonia) sex organs. Mobile, haploid, flagellated sperm are produced in the antheridium, and these swim to an archegonium to produce a fertilized zygote. The zygote can develop into a new, diploid sporophyte, thus completing the life cycle of the pteridophyte.


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