On leaf-arrangement

Abstract

Assuming, as generally known, the main facts of leaf-arrangement,— the division into the whorled and spiral types, and in the latter more especially the establishment of the convergent series of fractions, 1/2, 1/3, 2/5, 3/8, 5/13, 8/21, 13/24, 21/55, 34/89, 55/144, &c., as representatives of a corresponding series of spiral leaf-orders among plants, —we have to ask, what is the meaning that lies hidden in this law ? Mr. Darwin has taught us to regard the different species of plants as descended from some common ancestor; and therefore we must suppose that the different leaf-orders now existing have been derived by different degrees of modification from some common ancestral leaf-order.