Guilliermond - Atkinson 



— 162 



Cytoplasm 



pholipides reported by Reilhes) . In other cases the vacuoles take 

 on colors toward the violet. 



Dangeard used the characteristic shown by blue vital dyes, of 

 staining red or violet those vacuoles which contain metachromatin, 

 as the only basis for his theory of the universal presence of meta- 

 chromatin in vacuoles. But this staining reaction (Fr. metachro- 

 masie) is not a characteristic belonging alone to the substance called 

 metachromatin. Metachromatin has been so named because it 



Fig. 106. — Root of pea. A, meristem; chondrio- 

 somes (in) stained, vacuoles (P.V.) colorless. B, C, 

 meristem of central cylinder; contents of filamentous 

 vacuoles (P.V.) clearly distinguished from the chon- 

 driosomes by a peripheral hyaline region caused by 

 contraction of the contents of the vacuole by the 

 fixative. D, differentiated cortical parenchyma; 

 single large vacuole with densely stained bodies 

 (P.V.). m, chondriosomes. V, vacuole. Regaud's 

 method. 



changes all blue and violet aniline dyes and haematein to a red color 

 after fixation. Now this still unexplained phenomenon has no rela- 

 tion to the color change obtained with vital staining. One can not, 

 as do the Dangeards, relate the colloidal contents of all vacuoles to 

 a single substance and call it metachromatin, since metachromatin 

 is a substance present in fungi, so named by reason of a color 

 change which it shows after fixation, not when vitally stained. Be- 

 sides, it has been seen that metachromatin is preserved by alcohol 

 and formol, whereas the colloidal substance of the vacuoles is usu- 

 ally destroyed by all fixatives, even those of mitochondrial tech- 

 niques. 



If the blue coloration which the vacuoles sometimes take with 

 cresyl blue is often an index of an acid reaction, as is the case for 



