phyllotaxisn.

1845 A. Gray Bot. Text-bk. (ed. 2) i. v. 125 The spiral arrangement extends to all parts which are modifications of leaves, and is very apparent in the scales of the cones of Pines and Firs... The details of phyllotaxis are somewhat recondite, and do not appear to afford obvious applications of importance to structural or systematic botany.

1875 A. W. Bennett & W. T. T. Dyer tr. J. von Sachs Text-bk. Bot. 173 In a ²/ ₅ phyllotaxis..the 6th member stands over the 1st, the 7th over the 2nd, and so on.

1906 N.E.D. (at cited word) The principal kinds of phyllotaxis are (1) the cyclical or verticillate, in which a number of leaves (two or more) stand at the same level, forming a pair or whorl; and (2) the spiral or alternate, in which each leaf stands singly, their points of insertion forming a spiral (the genetic spiral) round the stem; in the latter case the phyllotaxis is expressed by a fraction denoting the angle (or portion of one turn of the spiral) between two successive leaves; thus in a ²/ ₅ phyllotaxis there are 5 leaves in every 2 turns of the spiral.

1946 A. Nelson Princ. Agric. Bot. vi. 111 Grasses..are readily separated from all other grass-like plants because their phyllotaxis is a half, while that of the non-grasses is one third.

1992 M. Ingrouille Diversity & Evol. Land Plants 41 The leaf arrangement, phyllotaxis, in orthotropic shoots is usually either spiral or in pairs opposite each other but with each successive pair at 90° to the former called a decussate arrangement.