Cell length variation in Phloem fibres within the bark of four tropical fruit trees Aegle Marmelos, Mangifera indica, Syzygium cumini, and Zizyphus mauritiana

Bark samples from collections made at monthly intervals during the calendar years 1973 and 1974, were studied to estimate the average length of phloem fibres in different positions within the bark of four tropical fruit trees, viz. Aegle marmelos Correa, Mangifera indica L., Syzygium cumini L., and Zizyphus mauritiana Lamk. In all the species studied, fibre elements found in the vicinity of vascular cambium are longer than those situated in the outer regions of the bark. The length variation of fibre elements is attributable partly to the increase in size of cambial initials with increasing age of the cambium and partly to the apical elongation of elements by intrusive growth.