Guilliermond - Atkinson 



160 



Cytoplasm 



visible, or of a very fluid hydrogel. Nevertheless this solution is 

 very unstable and easily precipitable, as we have seen in studying 

 the action of vital dyes on the vacuoles. Sometimes, however, the 

 large vacuoles of mature cells remain, as has been said, in the state 

 of a very concentrated colloidal solution, a sort of jelly. In this 



case, they are generally visible in 

 the ultramicroscope because of 

 their luminous contours. 



The filamentous vacuoles seem, 

 like the chondriosomes, to have a 

 specific weight rather like that of 

 the cytoplasm, although often it 

 is higher. For example, aker- 

 MAN found by use of the centri- 

 fuge that the filamentous vacuoles 

 existing under certain conditions 

 in the tentacles of Drosera are 

 heavier than the cytoplasm. H. 

 Clement, by the same process, 

 was not able to displace the chon- 

 driosome-shaped vacuoles contain- 

 ing anthocyanin in the teeth of 

 young rose leaflets. In recent work, 

 MiLOViDOV has shown that, in 

 the youngest cells of the teeth, the 

 chondriosome-shaped vacuoles con- 

 taining concentrated solutions of 

 tannin and anthocyanin become 

 oriented in the direction of the cen- 

 trifugal force and are therefore 

 heavier than cytoplasm. The large 

 vacuoles derived from them, and 

 containing a more dilute solution 

 of tannin, become oriented in the 

 opposite direction, i.e., centripetal- 

 ly, and are lighter than the cyto- 

 plasm. MiLOViDOV obtained simi- 

 lar results with barley roots. In 

 cells of the youngest part of the 

 meristem, the vacuoles are heavier 

 than the cytoplasm and are easily 

 displaced in the direction of cen- 

 trifugal force. In regions situated just a little above, the vacu- 

 oles which are beginning to take in water have about the same 

 density as the cytoplasm and are no longer displaced. In the region 

 in which the cells are already differentiated, the vacuoles are much 

 lighter than the cytoplasm and are displaced in a centripetal 

 direction. (Fig. 111). 



Thus the small vacuoles which look like the chondriosomes are 

 semi-fluid or sometimes almost solid elements. They seem to be 



fci? 



"# #■ 6 



Fig. 104. 



Filaments and oidia of 

 Endomyces Magnusii. Double vital staining 

 with Dahlia violet, which stains the chon- 

 driosomes (c), and with neutral red, which 

 colors the young vacuoles (1, V), or in 

 older vacuoles {V) causes precipitation of 

 their metachromatic substances as deeply 

 colored bodies. Gl, lipide granules. 



