Evert, Ray F. (U. Wisconsin, Madison.) Some aspects of cambial development in Pyrus communis. Amer. Jour. Bot. 48(6): 479–488. Illus. 1961.—The vascular cambium of pear is continually undergoing changes in composition and dimension. Circumferential growth occurs through oblique, anticlinal divisions of fusiform initials, followed by apical, intrusive growth. The production of new fusiform initials proceeds at rates which result in numbers of cells far in excess of those required for adequate circumferential expansion. Many of these cells are lost from the cambium, and others are transformed to ray initials. Consequently, a relatively low proportion of the new initials survive to repeat the cycle of elongation and division. New ray initials arise from existing ray initials and from fusiform initials. Although the immediate environment has a profound effect upon the fate of each cambial cell, over‐all cambial changes are obviously synchronized.