Bot. [f. TETRA- + Gr. ἀρχή beginning.] Proceeding from four distinct points of origin: cf. DIARCH.
1884. Bower & Scott, De Bary’s Phaner., 363. Triarch and tetrarch bundles sometimes occur in thick roots of species which are usually diarch. Ibid., 354. In the case of diarch and tetrarch structure of the main root.
1900. W. Wallace, in Ann. Bot., Dec., 643. The tetrarch or triarch root [of Actinostemma] has no pith and … no internal phloem.
B. sb. A stele containing four protoxylem groups.
1895. Vines, Students’ Text-bk. Bot., 179. The stele may have—in different structures—one to many protoxylem (primitive wood) groups, and is accordingly described as monarch … diarch … triarch … tetrarch … polyarch.
