prothallus

American  

[proh-thal-uhs] / proʊˈθæl əs /

noun

Botany.

• prothalli
  plural

1. prothallium.

---

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

---

prothallus Scientific  

/ prō-thăl′əs /

• prothalli
  plural

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

---

Other Word Forms

Derived Forms

• prothallic
  adjective

Inflected Forms

Nouns

• prothalli
  plural

Etymology

Origin of prothallus

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

Example Sentences

See Examples For:

prothallus

The large ones in germination produce a small prothallus; upon which the contents of the microspores act in the same way as in Ferns, and with a similar result.

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

When the prothallus of a fern has developed normally, it is a flattened leaf-like structure which bears rootlets and male and female genital organs on the lower surface, i.e., on that turned from the light.

From The Biological Problem of To-day Preformation Or Epigenesis? The Basis of a Theory of Organic Development by Oscar Hertwig

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 Asa Gray

Similarly in the Araucarieae and in Widdringtonia the archegonia are numerous and scattered and often sunk in the prothallus tissue.

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

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