Chapter XVI — 189 — Role of Vacuoles 



such a way that it is always hypertonic with regard to the sur- 

 rounding medium. As soon as the concentration of the latter 

 increases, the cells hydrolize their reserve starch and the resulting 

 sugar goes into the vacuolar sap whose osmotic capacity increases. 

 This phenomenon has been given the name anatonosis. The pres- 

 ence of colloidal substances in the vacuole suggests that their role 

 is not reduced merely to osmotic actions but that they intervene 

 also in the processes of the passage of water in and out of the cell. 

 It is, in fact, this inward and outward passage of water, inter- 

 vening alternately between vacuolar colloids and cytoplasmic col- 

 loids which explains the reversibility of form of the vacuolar sys- 

 tem discussed earlier. 



The vacuoles are accumulation regions, the reservoirs of a large 

 number of metabolic products or of reserves, and are particularly 

 regions of excretion of toxic substances, as the action of vital dyes 

 tends to indicate. In the vacuoles, there accumulate all the products 

 secreted by the cell which can be dissolved in water, forming true 

 or pseudosolutions (proteins, holosides, heterosides, tannins, fla- 

 vins, oxyflavanol and anthocyanin pigments, organic acids, alka- 

 loids, certain lipides, mucilages and so on). These various prod- 

 ucts may appear in the meristematic cells at the very beginning 

 of development of the vacuolar system, or at any stage whatever, 

 during the development of the system. It has been possible to 

 demonstrate, notably by microchemical reactions, that in the seed- 

 ling of tobacco, alkaloids appear in the cells of the meristem of 

 the root, in the chondriosome-shaped vacuoles formed by the hydra- 

 tion of aleurone grains (Chaze). There have been localized also 

 in the chondriosome-shaped vacuoles of the meristematic cells, cer- 

 tain heterosides, such as the saponarosides (POLITIS). This is 

 true for tannins (GuiLLlERMOND, P. Dangeard), the oxyflavanol 

 compounds and anthocyanin pigments (Guilliermond) . The vacu- 

 olar system is certainly more than a locus for the accumulation of 

 these various products. The presence of colloidal substances in 

 the vacuoles and their predilection for vital stains lead us to sup- 

 pose, as do the Dangeards, that the vacuoles can exercise a role 

 in absorption phenomena because of these very properties of ab- 

 sorption, imbibition and combination which bring about the pene- 

 tration of the dyes. Devaux believes the vacuolar system to be 

 the site of chemical affinities of the cell and explains that the vital 

 dyes penetrate the cell without staining the protoplasm and accu- 

 mulate exclusively in the vacuoles, i.e., in the non-living parts of 

 the cell, because the chemical affinities of the living substance are 

 masked by reciprocal saturation. So by his theory of polarized 

 (catalytic) membranes (C/. p. 121) only the non-living inclusions of 

 the cytoplasm, such as the vacuoles, are capable of fixing the dyes, 

 and there is localization of protoplasmic activity on the surface 

 presented by the protoplasm and the vacuole. It has been seen 

 that this opinion is not justified. If, actually, some dyes, like 

 neutral red, traverse the cytoplasm without ever staining it and 

 accumulate only in the vacuole, this is not true for other dyes which 



