Guilliermond - Atkinson 



— 184 



Cytoplasm 



to be attributable to the viscosity of their contents, since the co- 

 existing vacuoles without colloidal substances are always spherical. 

 In all cases in which the cells contain two categories of vacu- 

 oles, these vacuoles become distinct very early and it is very diffi- 

 cult to determine their origin. It would seem, however, that the 

 vacuoles lacking in colloidal substances arise by exudation from 

 vacuoles rich in colloids, for, by plasmolysis, it is possible in some 

 cases to obtain experimentally the formation of similar small vacu- 

 oles in cells which do not contain any. 



It would be natural, therefore, along 

 with Weber and Kuster, to relate this 

 phenomenon to vacuolar contraction and 

 to attribute it to a syneresis assuming that 

 the vacuoles not staining with vital dyes 

 are totally lacking in colloidal substances. 

 But we have seen that this is not always 

 so and in the fruit of the blackberry there 

 exist two categories of vacuoles both of 

 which contain colloidal substances. In 

 this case it might be supposed that these 

 two categories of vacuoles, which seem to 

 correspond to small accumulation and 

 transportation centers for various meta- 

 bolic products, are always distinct and 

 have no genetical connection, or else that 

 they arise by a differentiation from a 

 single category of vacuoles, but by the 

 phenomenon of coacervation and not of 

 syneresis (Cf. p. 177). 



However this may be, this last ex- 

 planation does not apply to the lower 

 plants, in particular to the algae, in which 

 there are encountered still more fre- 

 quently, several categories of vacuoles in a 

 single cell. In the brown algae it has been 

 known for a long time that there exist 

 viscous inclusions which have been called 

 fucosan granules (Hansteen), or phy- 

 sodes (Crato), whose morphological sig- 

 nificance has been the subject of numerous 

 discussions. These inclusions stain vitally like the vacuoles and 

 yet are present at the same time with other large vacuoles whose 

 contours are more fluid and which also take the vital dyes but 

 stain differently. Cresyl blue, for example, gives the inclusions 

 a greenish blue tint, whereas the vacuoles take a violet-blue color. 

 These inclusions contain in fact catechin tannins, showing the 

 phloroglucinol-hydrochloric test, which explains the greenish blue 

 color which they give to cresyl blue. Although these phenolic in- 

 clusions are always separated from the other vacuoles even in the 

 beginning, it seems logical to consider them, as does Mangenot, 



Fig. 128. — Fig. Living 

 cells from the inner part of 

 the fleshy receptacle. Two 

 types of vacuoles, one (V) 

 varying in size and shape 

 with colloidal contents and 

 anthocyanin pigment; the 

 other iv) , varying in size 

 but always spherical, with- 

 out colloidal substance. 



