prothallus

[ proh-thal-uhs ]

noun

, Botany.

, plural pro·thal·li [proh-, thal, -ahy].

1. prothallium.

prothallus

/ 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

/ prō-thăl′əs /

, Plural prothalli prō-thăl′ī

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

Derived Forms

• proˈthallic, adjective

Word History and Origins

Origin of prothallus¹

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

Word History and Origins

Origin of prothallus¹

C19: from New Latin, from pro- before + Greek thallus a young shoot

Example Sentences

Prothallus underground, not green, monœcious.—A small order, separated from Ferns on account of the different nature of the sporangia, the erect vernation, etc.

From Project Gutenberg

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

From Project Gutenberg

Antheridia or archegonia, or both, formed upon the stem or branches of the plant itself, which is developed from the germinating spore usually with the intervention of a filiform or conferva-like prothallus.—Divided into the Musci, or Mosses, and the Hepaticæ.

From Project Gutenberg

Antheridia or archegonia, or both, formed on a minute prothallus which is developed from the spore on germination, the archegonium containing a nucleus, which after fertilization becomes an oöspore and at length grows into the conspicuous spore-bearing plant.

From Project Gutenberg

Prothallus green, formed upon the ground, often variously lobed, usually diœcious.

From Project Gutenberg