Chapter XIII 



— 135 — 



Vital Staining 





This reduction is observed between slide and cover glass and 

 in tissue incapable of development. It is probable that under nor- 

 mal conditions, i.e., in culture or in an organ capable of growth, 

 the rose derivative, once formed, accumulates in the vacuoles be- 

 fore the growth of the tissue. 



It has been seen that in Saprolegnia similar phenomena take 

 place. In many fungi, however, especially in the yeasts, Janus 

 green may be taken up by the cytoplasm at the same time as by 

 the chondriosomes, then be reduced there to its rose derivative (or 

 even to its leucoderivative in anaerobic conditions) and this deriva- 

 tive is later excreted into the vacuole. 



Among the dyes of the second group are some which are toxic, 

 for example naphthylene blue and naphthylamine blue. There are 

 others which are less so, such as cresyl 

 blue and especially Nile blue. Finally, 

 there are still others which are a very 

 little toxic — neutral red and neutral 

 violet, by far the least toxic of all these 

 vital dyes. All these vital dyes pro- 

 duce coloration of the vacuoles which, 

 as will be seen further on, is essen- 

 tially a vital phenomenon, for it is pos- 

 sible only during the life of the plant. 



Neutral red and neutral violet are 

 closely allied dyes. They behave in the 

 same manner and are particularly in- 

 teresting. From our research on the 

 behavior of neutral red, it is found 

 that except in rare cases, the dye is 

 not retained by the cytoplasm and that 

 the coloration of the living cell which 

 results, is almost always strictly lim- 

 ited to the vacuoles (Fig. 85) . We have 

 found only a few rare yeasts in which 

 neutral red may color certain lipide in- 

 clusions of a very special nature at the same time as the vacuoles, 

 although we have examined a considerable number of cells belong- 

 ing to the phanerogams and to the most diverse fungi observed 

 with the aid of this stain. In the Myxomycetes, however, Man- 

 GENOT showed that neutral red colors certain sphaerocrystals of a 

 phenolic nature. In the algae, some mucilaginous inclusions are 

 known with which tannins are often associated, which are stained 

 by the vital stains at the same time as the vacuoles. But it appears 

 that these inclusions, to be taken up later, may be considered as 

 vacuoles of a special nature. 



The different phases of staining the living cell with neutral red 

 may be followed under the microscope. The vacuoles, as we have 

 said, appear in various forms. They may be small and contain 

 colloidal substances in very concentrated solutions, as in embryonic 

 cells, or they may be very large and contain a very dilute colloidal 



M 



C 1 



Fig. 86. — Penicillium glau- 

 cum. Vital staining with neutral 

 red. A, B, C. 1, precipitates 

 in vacuole; 2, migration of pre- 

 cipitates into cytoplasm. D, 

 1-5, stages observed in a single 

 vacuole. 



