a. (Chem.) Of or pertaining to thallium; derived from, or containing, thallium; specifically, designating those compounds in which the element has a lower valence as contrasted with the thallic compounds. [ Written also thallious. ] [ 1913 Webster ]
‖n.; pl.Thalli [ NL., fr. Gr. &unr_; young shoot or branch, frond. ] (Bot.) A solid mass of cellular tissue, consisting of one or more layers, usually in the form of a flat stratum or expansion, but sometimes erect or pendulous, and elongated and branching, and forming the substance of the thallogens. [ 1913 Webster ]
‖n.; pl.Thalli [ NL., fr. Gr. &unr_; young shoot or branch, frond. ] (Bot.) A solid mass of cellular tissue, consisting of one or more layers, usually in the form of a flat stratum or expansion, but sometimes erect or pendulous, and elongated and branching, and forming the substance of the thallogens. [ 1913 Webster ]