Archive image from page 142 of The cytoplasm of the plant. The cytoplasm of the plant cell cytoplasmofplant00guil Year: 1941 Chapter XII — 127 — The Vacuoles tiated membrane, and are endowed with properties of secretion. It is this membrane to which DE Vries gave the name tonoplast, which he beheved secreted all the substances dissolved in the vacuolar sap. De Vries, moreover, thought that the vacuoles can not in any case form de novo, but are always transmitted by divi- sion from cell to cell, like the nucleus and plastids. In short, DE Vries compared the vacuoles to a sort of liquid plasti
Archive image from page 142 of The cytoplasm of the plant. The cytoplasm of the plant cell cytoplasmofplant00guil Year: 1941 Chapter XII — 127 — The Vacuoles tiated membrane, and are endowed with properties of secretion. It is this membrane to which DE Vries gave the name tonoplast, which he beheved secreted all the substances dissolved in the vacuolar sap. De Vries, moreover, thought that the vacuoles can not in any case form de novo, but are always transmitted by divi- sion from cell to cell, like the nucleus and plastids. In short, DE Vries compared the vacuoles to a sort of liquid plastid to which VAN TiEGHEM gave the name hydroleucites. At the time that DE Vries did his work, however, the origin of vacuoles was unknown. All that was known, and had been known for some time, was that several vacuoles appear scattered about in the cytoplasm of cells which are beginning to differentiate; that they enlarge and then coalesce until in mature cells there is only one enormous vacuole occupying the entire cell, pushing the cyto- plasm and the nucleus back to the periphery. Aside from this, noth- ing was known. As a matter of fact, it is generally impossible to distinguish the vacuoles in living embryonic cells. Hence, in the opinion of the earlier botanists, the vacuoles were lacking in these cells and formed de novo in the course of cellular differentiation, as seems to be indicated in figure 82, reproduced here from Sachs. Went, a student of de Vries, succeeded, however, in revealing in embryonic cells of certain plants, the existence of small vacuoles vvhich increase in num- bers by fission. This seemed to in- dicate that the vacuoles do not arise de novo, but keep their individuality during the course of de- velopment, and consequently seemed to support the thesis of DE Vries. This theory, nevertheless, was not based on sufficiently solid facts. It has not, as a matter of fact, been possible to bring out the vacuolar membrane by means of stains and its existenc
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