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Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar . An independent sporophyte is the dominant form in all clubmosses , horsetails , ferns , gymnosperms, and angiosperms that have survived to the present day.
Rhynia is a single-species genus of Devonian vascular plants. Rhynia gwynne-vaughanii was the sporophyte [2] generation of a vascular, axial, free-sporing diplohaplontic embryophytic land plant of the Early Devonian that had anatomical features more advanced than those of the bryophytes.
The species Folioceros fuciformis and the genera Megaceros, Nothoceros and Dendroceros have short-lived spores with thin and colorless walls that appear green due to the presence of a chloroplast. [ 19 ] [ 20 ] In most species, there is a single cell inside the spore, and a slender extension of this cell called the germ tube germinates from the ...
Conocephalum is a genus of complex thalloid liverworts in the order Marchantiales and is the only extant genus in the family Conocephalaceae. [1] [2] Some species of Conocephalum are assigned to the Conocephalum conicum complex, which includes several cryptic species. [1]
The sporophyte of a flowering plant is often described using sexual terms (e.g. "female" or "male") based on the sexuality of the gametophyte it gives rise to. For example, a sporophyte that produces spores that give rise only to male gametophytes may be described as "male", even though the sporophyte itself is asexual, producing only spores.
The microspores of both exosporic and endosporic species are free-sporing, distributed by wind, water or animal vectors, but in endosporic species the megaspores and the megagametophyte contained within are retained and nurtured by the sporophyte phase. Endosporic species are thus usually dioecious, a condition that promotes outcrossing.
Certain species of brown algae can also perform asexual reproduction through the production of motile diploid zoospores. These zoospores form in plurilocular sporangium, and can mature into the sporophyte phase immediately. In a representative species Laminaria, there is a conspicuous diploid generation and
The rhyniophytes included "protracheophytes", which were precursors to vascular plants (e.g., Horneophyton, Aglaophyton); basal tracheophytes (e.g., Stockmansella, Rhynia gwynne-vaughanii); and plants allied to the lineages that led to the living club-mosses and allies as well as ferns and seed plants (e.g., Cooksonia species).