prothallus

American  

[proh-thal-uhs] / proʊˈθæl əs /

noun

Botany.

plural

prothalli

1. prothallium.

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prothallus British  

/ prəʊˈθælɪəm, prəʊˈθæləs /

noun

1. botany the small flat free-living gametophyte that bears the reproductive organs of ferns, horsetails, and club mosses. It is either a green disc on the soil surface or it is colourless and subterranean

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prothallus Scientific  

/ prō-thăl′əs /

plural

prothalli

1. The gametophyte of homosporous ferns and some other plants. Prothalli have chlorophyll for photosynthesis, but they are not differentiated into roots, stems, or leaves. They are usually small, flat, and delicate. Prothalli develop from germinated spores, and they bear both archegonia for producing eggs and antheridia for producing sperm.

2. See more at alternation of generations

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Other Word Forms

• prothallic adjective

Etymology

Origin of prothallus

From New Latin, dating back to 1850–55; pro- ², thallus

Example Sentences

When the sporules are produced, the protospore, somewhat analogous to a prothallus, has performed its functions and decays.

From Fungi: Their Nature and Uses by Cooke, M. C. (Mordecai Cubitt)

Microspore spherical or oval, with or without a bladder-like extension of the exine, containing a prothallus of two or more cells, one of which produces two non-motile or motile male cells.

From Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" by Various

Investigation of this prothallus under the microscope resulted in the discovery of a wholly unsuspected kind of fertilization, taking place at this germinating stage of the plant.

From The Elements of Botany For Beginners and For Schools by Gray, Asa

The embryo of Gnetum forms an out-growth from the hypocotyl, which serves as a feeder and draws nourishment from the prothallus.

From Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" by Various

In germination they develop a minute prothallus which bears archegonia to be fertilized by antherozoids developed from the microspores.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Gray, Asa