The secretory cells arc a prominent component of the phloem tissue of Mimosa pudica L. They form longitudinal files in which the common end walls of the cells are perforated. The origin of the perforations in relation to protoplast differentiation was the objectof the study. As the cells emerge from the meristematic state, portions of cytoplasm including some organelles aretransferred into the central vacuole and are apparently lysed. This phenomenon is accompanied by an accumulation of flocculent material, possibly the secretory product referred to in the literature as a carbohydrate. The tonoplast ceases to be definable so that the flocculent materialand degraded and non-degraded protoplast components are intermingled inthe cell lumen. The perforation of the end wall OCCUR while the tonoplast is still intact. Theplasmalemmas of the contiguous cells withdraw from the part of the wall undergoing degradation. The space becomes filled with fibrous debris of the apparently lysed wall. The degraded wallpart becomes broken possibly by a unidirectional pressure flow in the cells, for the remnants of the wall are pushed into one of the two superimposed cells. At this presumably mature stage, the cells contain someintact protoplast components among which ribosomes are especially conspicuous.