Characters of Cells Attaining Great Age

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Abstract
The medullary cells of Ferocactus wislizenii attain full size within the 1st decade, undergoing some change in form but no measurable change in volume during the following century. During the 1st decade the cells of the cortex increase 40-fold in cross sectional area, but on account of slow growth their areas are only doubled in the century following. Unlike Carnegia neither the cells of the medulla nor those of the cortex retain their meristematic capacity for more than 10 yrs. Changes in ph in hydrating solutions show maximum distention and minimum permeability in both young and old cells of the medulla, with the minimum at pn 2-3 and the maximum at pH 10-11. Medullary cells exhibit high distensibility following low permeability in Ca solutions of 0.001 [image], with lesser effects in similar K solutions. The maximum distention of cortical cells varies with Ph, being nearer the neutral point than in those of the medulla. The critical regions are not well defined in old cortical cells. Definite distention of both young and old cortical cells, indicating minimum permeability, occurs in K solutions at 0.01-0.001[image], while effects in Ca solutions on medullary cells are not marked. Compared with the effects of Ca on medullary cells, these results may be explained on the basis of different tissue constituents. The relative dry weight of medullary cells increases with age while that of cortical cells decreases. Carbohydrates increase with age in both cortex and medulla. Permeability of cell-masses in both cortex and medulla increases with age, incident to wasting of protoplast and accentuation of cell wall perforations. Pentosans of the protoplasm are depleted in senescence and lipoids and proteins undergo less change with age. Increase in crystals and other insoluble inclusions occurs with age in cells of both medulla and cortex. Total titratable acidity shows a diminution with age, as would be expected if carbohydrates are used in respiration.

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