Guilliermond - Atkinson — 220 — Cytoplasm 



As the plastids have, furthermore, histochemical and histo- 

 physical characteristics entirely similar to those of the chondrio- 

 somes (viscosity, manner of alteration, refraction, behavior in 

 regard to fixatives and stains), it is legitimate to put them in the 

 same category. The plastids may be considered as a supplementary 

 category of chondriosomes connected with the photosynthetic func- 

 tion which characterizes green plants. Hence we are led to think 

 that the ordinary chondriosomes and the plastids, by virtue of 

 their finely divided state in the cytoplasm, are the seat of impor- 

 tant surface phenomena and that they have a similar general func- 

 tion, of which that shown by the plastids is one manifestation. 



Vacuolar system or vacuome:- The vacuolar system, or vacu- 

 ome, is represented in embryonic cells of most plants by numerous 

 minute inclusions of semi-fluid consistency composed of a very 

 concentrated colloidal solution (in the state of a hydrogel or co- 

 acervate). In their forms (granules, isolated or assembled in 

 chains, undulating filaments often anastomosing into a network), 

 they sometimes greatly resemble the chondriosomes. These inclu- 

 sions are occasionally visible in living material because they are 

 more refractive than the cytoplasm, or because they contain antho- 

 cyanin pigments which give them a natural color. They are most 

 diflftcult to distinguish under the ultramicroscope, for here they 

 look like chondriosomes. They can be easily brought out with 

 vital stains (neutral red, cresyl blue, Nile blue), for which they 

 have a strong predilection. They are stained homogeneously and 

 deeply by these dyes without precipitation of the enclosed colloids. 

 They have, however, less affinity for chondriosomal stains (Janus 

 green. Dahlia violet and methyl violet) which, nevertheless, also 

 stain them when they contain substances capable of retaining these 

 dyes, in particular phenol compounds, and when the dyes used 

 are of certain concentrations. In the course of cellular differentia- 

 tion, these elements swell because they contain colloids in pseudo- 

 solution whose capacity for taking in water is much greater than 

 that of the cytoplasm. Thus they are transformed into small, 

 spherical, increasingly fluid vacuoles (vacuoles in the classical 

 sense) . There has taken place, therefore, a transformation of the 

 very condensed colloidal substance, of which they seem to have 

 been formed, into a very dilute solution. The vacuoles may later 

 fuse so that, in the mature cells, there is formed a single enormous 

 vacuole. As they become liquid, the vacuoles cease to stain homo- 

 geneously and deeply with vital stains, and their colloids are pre- 

 cipitated as deeply colored corpuscles showing Brownian movement 

 in the vacuolar sap. This last remains colorless, or takes a diffuse 

 tint. Sometimes the dyes do not cause a precipitation and the vacu- 

 olar sap stains only diffusely. In certain cases, as they swell and 

 fuse together, the colloidal solutions of the young chondriome-shaped 

 vacuoles continue to be very concentrated, and the large vacuole 

 of the mature cells continues to have a colloidal content in the 

 state of a hydrogel or of an almost solid gel which, by syneresis, 



