Guilliermond - Atkinson 



154 — 



Cytoplasm 



Rather often, there are normally found in the vacuoles more 

 or less large, spherical bodies, or small granules united in mul- 

 berry-shaped masses, which are the result of a partial precipita^ 

 tion of the colloidal solution within the vacuoles. These bodies 

 stain with vital dyes which, at the same time, bring about other 

 precipitates of the same or of different natures. The normal pres- 

 ence of these bodies in the vacuole could be explained by the fact 

 that the colloidal micelles contained in the vacuoles in some cases 

 do not possess a power of unlimited imbibition, so a time seems 

 to come when they cease to take in water. A disturbance in equi- 

 librium occurs and this leads to the production in the vacuolar 

 sap of a coacervate. 



It may be added that rather frequently the large vacuoles of 

 mature cells, especially when they contain tan- 

 nins, continue to enclose a very concentrated so- 

 lution and in living material are exceedingly 

 refractive. These vacuoles which seem to be in 

 the state of a jelly do not form precipitates with 

 vital dyes or else form them with great difficulty. 

 In the latter case they show an intense homo- 

 geneous color. There are even cases in which the 

 jelly is almost solid and in such cases it becomes 

 very difficult to plasmolyze the cells, as is seen 

 in the vacuoles of the pericarp of Ilex Aquifolium 

 (Guilliermond, Chaze). 



Vacuoles behave differently according to the 

 nature of their contents. 



The development of the vacuolar system which 

 we have just described is of very general occur- 

 rence and has been observed in very widely sep- 

 arated plants (phanerogams: P. A. Dangeard, 

 Guilliermond, P. Dangeard, Bailey, Zirkle and 

 others; pteridophytes : Emberger). 



All the vacuoles of the higher plants however, 

 do not follow exactly this development. Thus, in 

 studying the formation of the vacuoles in the bud of Elodea canor- 

 densis, it is observed that in all the cells of the meristem of the 

 stem and of the youngest foliar primordia, there are numerous, very 

 small vacuoles which are always globose and never filamentous. 

 These generally stain uniformly and deeply with neutral red, but 

 in certain cases there is seen in their interior a single, deeply 

 stained, corpuscle showing Brownian movement. This corpuscle 

 has been produced by a precipitation of the colloidal contents of 

 the vacuole. These vacuoles, which are not visible in living mate- 

 rial without being stained, seem to be constituted of a less concen- 

 trated colloidal solution than are those in ordinary cases. They 

 later swell up by taking in water and then gradually coalesce to 

 form, in mature cells, a single vacuole which neutral red stains 

 diffusely while also causing the production of numerous precipi- 

 tates. There are, therefore, no filamentous or reticulate formations 



Fig. 98. — Bud of 

 Elodea canadensis vi- 

 tally stained with 

 neutral red. Vacu- 

 oles globular and uni- 

 formly stained; or 

 small and colorless 

 with one or several 

 colored precipitates. 



