Chapter XIV — 161 — The Vacuolar System 



composed of a jelly or of a coacervate. One is therefore led to 

 believe that the development of the vacuoles described in the pre- 

 ceding pages may possibly be nothing more than an unlimited 

 imbibition of small elements, shaped like granules or filaments, 

 which are in a jellied or coacervate state. This imbibition would 

 involve the transformation of the original gel into a very dilute 

 solution represented by the liquid vacuoles. 



Chemical nature of the colloidal substance of vacuoles:- The 

 histochemical characteristics of young vacuoles, which we have 

 enumerated to establish a distinction between the chondriosome- 

 shaped vacuoles and the chondriosomes themselves, prove that the 



M 







Fig. 105. — Ricinus root. Meristem fixed by 

 Regaud's method. Black, filamentous or granular 

 chondriosomes (Ch) and vacuoles (V) , the latter 

 distinguished by an external hyaline region due 

 to a contraction of their colloidal contents during 

 fixation. 



colloidal substances of the vacuolar sap have an essentially variable 

 constitution. Vacuoles are present in all plants but there does 

 not exist any substance characteristic of them, as is the case for 

 the chondriosomes. They contain diverse substances having noth- 

 ing in common except their property of fixing vital stains. 



Vital staining alone reveals differences in coloration between 

 vacuoles. Cresyl blue, for example, changes color in vacuoles 

 which contain metachromatin (majority of fungi, certain algae). 

 It stains them a diffuse red and the enclosed corpuscles are colored 

 dark red. In the cells of phanerogams, the staining of the vacu- 

 oles is extremely variable. Whenever the vacuoles contain phe- 

 nolic compounds, they take a pure blue color with cresyl blue be- 

 cause of their acid pH. This same blue color is sometimes observed 

 when the vacuoles contain lipide substances (phytosterol or phos- 



