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; see origin at pro- ², thallus

Example Sentences

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

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

The seed-like structure afforded protection to the prothallus, and may have enabled the embryo to be launched on the world in greater security.

From Darwin and Modern Science by Seward, A. C. (Albert Charles)

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

A young prothallus of a Maiden-hair, moderately enlarged, and an older one with the first fern-leaf developed from near the notch.

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