Chapter XIV 



— 163 — 



The Vacuolar System 



the vacuoles containing phenolic compounds, the red or violet 

 coloration which they take in other cases is difficult to explain, for 

 it is known that cresyl blue in solution in pure water shows only 

 a single change in color : it takes on an orange tint for a pR value 

 of 11.2. Nevertheless, according to Mangenot and Mile Laurent, 

 cresyl blue at a pB. which is not accurately measured, shows a 

 change to violet, on condition that the medium contain diverse 

 colloidal substances (sodium silicate, dextrine, protein, etc.) or 

 even sugar (saccharose, according to unpublished work). This 

 fact has been confirmed by Chadefaud. 



VCM 9''-^ 



immk 



I 





! 4 M 



■■■ ¥1 



.Ch 



1 



mm 



2 







HmfL 







Fig. 107 (left). — Dematium. Bouin's method, stained with hemalum. 1, filament. 2, 

 germinating conidium. VCM, vacuole containing metachromatin precipitates, n, nucleus. 



Fig. 108 (right). — Saprolegnia. Chondriome and vacuolar system. 1-3, Vital staining 

 with neutral red. 1, tip of filament; reticular vacuole (RV) ; other elements omitted. 2, older 

 filament; tendency of network to become a diffusely stained canal (V) containing deeply 

 stained bodies (CM), other elements visible but unstained. 3, still older filament; vacuolar 

 canal (V) loses its stain, other bodies as in (2). 4, mature filaments. Regaud's method 

 with iron haematoxylin; vacuolar canal unstained, lipide granules dissolved, chondriosomes 

 (Ch) strongly stained. 5, 6, mature filament. Meves' method with acid fuchsin; chondriosomes 

 (Ch) red, lipide granules (Gg) brown. Ch, chondriosomes. N, nucleus. 



It must be added that the change to red in the vacuoles may 

 also depend on the chemical constitution of colloidal substances 

 which the vacuoles hold in solution. Mucilaginous substances, agar, 

 for instance, change cresyl blue to a color toward the red, no mat- 

 ter what the pH. According to LisoN, this color change in vital 

 staining is a histochemical reaction characteristic of all sulfuric 

 esters of high molecular weight. Now, mucilages or polyholoside 

 esters are the most important among them. 



From these considerations it follows, therefore, that the change 

 toward red of the vacuoles, which is due to the most variable 

 causes, and which may be obtained in vitro by the addition of the 

 most diverse substances, can not possibly serve to characterize a 

 chemical substance. 



In general, the vacuolar colloids appear in the higher plants 

 to be protein substances, perhaps proteins soluble in alcohol, and 



