Chapter XV 



173 — 



Origin of Vacuoles 



plete dehydration leads finally to the transformation of these semi- 

 fluid vacuoles into solid bodies (aleurone grains) by a solidification 

 of their colloids. The aleurone grains, by taking up water anew, 

 are capable of again assuming the semi-fluid consistency and ap- 

 pearance of chondriosomes and, by a continuance of this process, 

 may finally become liquid vacuoles. 



The filamentous appearance of the vacuoles seems to be the 

 result of their semi-fluid state, for in the semi-fluid state, the 

 vacuoles are generally filamentous or reticulate and stain uniformly 

 and deeply with vital dyes. In the liquid state, the vacuoles are 

 generally spherical and are stained only weakly with the vital dyes, 

 which bring about a precipitation of the enclosed colloids as deeply 

 stained granulations showing Brownian movement. The vacuoles 

 are then composed of drops of a very dilute colloidal solution. In 



Fig. 120. — Saprolegnia. Modifications in form of vacu- 

 olar system in a single branch, cultivated on 1% peptone 

 bouillon with 0.001% neutral red, in a van Tieghem and 

 Le Monnier cell. 1-6, spherical vacuoles fuse to form a 

 single canal which then, 7, 8, is transformed into a net- 

 work (After Mile. Cassaigne). 



the solid state, they appear as globular bodies, which do not stain 

 with vital dyes unless imbibition has previously taken place, but, 

 on the contrary, always stain after fixation. The vacuoles, there- 

 fore, may pass from one form to the other depending upon the 

 water content of the cell. 



This reversibility has been obtained experimentally, further- 

 more, in various cells, among others, in the epidermal cells of peri- 

 anth parts of red tulips (Fig. 119). In the open flower, these cells 

 contain a large vacuole, occupying almost the entire volume of the 

 cell, and containing a concentrated solution of red anthocyanin pig- 

 ment. Now, by plasmolyzing mature epidermal cells with a strongly 

 hypertonic solution, we have observed that these vacuoles, as they 

 lose water, may break up into small vacuoles which become semi- 

 fluid and appear granular, filamentous and reticulate. Similar re- 

 sults have been obtained in the Saprolegniaceae (Guilliermond) 

 and in the epidermal scales of Allium Cepa (Kuster) . 



