American Heritage® Dictionary of the English Language, Fourth Edition
- n. A plant body undifferentiated into stem, root, or leaf.
Century Dictionary and Cyclopedia
- n. In botany, a vegetative body or plant-body undifferentiated into root, stem, or leaves; the plant-body characteristic of the Thallophyta. Also thalamus. See cut under applanate.
- n. botany An undifferentiated plant body, such as in algae.
- n. botany Any plant body lacking vascular tissue.
GNU Webster's 1913
- n. (Bot.) A solid mass of cellular tissue, consisting of one or more layers, usually in the form of flat stratum or expansion, but sometimes erect or pendulous, and elongated and branching, and forming the substance of the thallogens.
- n. a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes
- From Ancient Greek θαλλός (thallos, "young shoot, twig"). (Wiktionary)
- Latin, green stalk, from Greek thallos, from thallein, to sprout. (American Heritage® Dictionary of the English Language, Fourth Edition)
“Rapid water loss inactivates the thallus, and in the inactive state the lichen is safe from heat-induced respiratory loss and heat stress .”
“Photorepair of radiation-damaged DNA in Cladonia requires not only light, but also high temperature and a hydrated thallus .”
“Most lichens are adapted to such effects by forming a mechanically solid thallus firmly attached to the substrate.”
“Buffoni Hall et al.  demonstrated that in Cladonia arbuscula ssp. mitis an increase in phenolic substances is specifically induced by UV-B radiation, and that this increase leads to attenuation of the UV-B radiation penetrating into the thallus.”
“However, the sensitivity of spores is not equivalent to the sensitivity of the metabolic machinery of the vegetative body of a fungus (i.e., the thallus or mycelium) that produces the spores.”
“CO2 exchange and thallus nitrogen across 75 contrasting lichen associations from different climate zones.”
“In the latter case, small powdery clusters of hyphae and algae, called soredia are formed and cut off from the thallus as it grows.”
“The fungus and algal cells of lichens are associated together in a spongy thallus which can range in diameter from less than 1 millimeter (mm) to more than 2 meters (m).”
“The thallus consists of 3 or 4 layers of cells or hyphae.”
“These are plants growing in sea or fresh water, or on damp surfaces, with a filamentous, or more rarely a leaf-like pulverulent or gelatinous thallus; the last two forms essentially microscopic.”
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