Guilliermond - Atkinson — 132 — Cytoplasm 



has shed considerable light on this question. The essential results 

 will be summarized here as briefly as possible. 



It appears, as Kuster had already noticed, that living plant 

 cells are permeable to a great number of vital dyes. These may 

 accumulate in all the vacuoles, whatever their content. Others, 

 such as methylene blue, Bismarck brown and chrysoidine, may 

 stain the cytoplasm and the nucleus and may accumulate in the 

 vacuoles, but only if the vacuoles contain phenol compounds (tan- 

 nin, oxyflavanol and anthocyanin pigments). The cytoplasm and 

 nucleus are particularly easy to stain with chrysoidine. 



In general it is only the basic dyes which penetrate living cells. 

 Under some conditions, however, some acid dyes will do this, but 

 the greater number of the dyes are not of importance in the ques- 

 tion which occupies us. 



There are only a small number of vital dyes, all of them basic, 

 which are capable of being used for the study of morphological 

 constituents of the cytoplasm and these may be divided into two 

 groups from the point of view of their action on plant cells: 



1. Dyes, which like Janus green. Dahlia violet, methyl violet 

 and a certain number of others, at first stain the chondriosomes 

 and plastids, for which they have an affinity, but can also under 

 some conditions accumulate in the vacuoles. (Among these dyes, Bis- 

 marck brown and methylene blue are very slightly toxic. We have 

 been able to germinate grains of wheat and have made Saprolegnia 

 grow in media to which these dyes have been added in proportions 

 from 0.0005-0.02%. In young wheat roots, as well as in Sapro- 

 legnia, the vacuoles which stain only between slide and cover glass 

 and only under certain conditions (especially when they enclose 

 phenolic compounds), accumulate the dyes during growth. Chry- 

 soidine, beginning with solutions of 0.005% is, on the contrary 

 very toxic). 



2. Dyes, which, like neutral red, neutral violet, cresyl blue, 

 Nile blue, naphthylene blue and naphthylamine blue, do not stain 

 the chondriosomes and plastids but, under normal conditions, ac- 

 cumulate exclusively in the vacuoles. 



The dyes of the first group are very toxic and do not produce 

 vital staining except when employed in solutions of low concen- 

 tration. At higher concentrations they are taken up by the chon- 

 driosomes in cells which remain alive for some time as shown by 

 their cytoplasmic currents, but in these cells the dyes rapidly cause 

 death. The staining is, therefore, sublethal. Recent work (Guil- 

 liermond and Gautheret) has shed a good deal of light on the 

 question of vital staining of leucoplasts and chondriosomes, which 

 until now had been rather obscure. This work has shown, as has 

 been already seen, that a certain number of dyes may be taken up 

 at first by the cytoplasm and nucleus, or by the chondriosomes and 

 leucoplasts, but this staining is purely transitory and the dye goes 

 into the vacuole very quickly. It is only when the cells have ex- 

 creted the stain into the vacuoles that the cells are capable of grow- 

 ing and multiplying. 



