The Staining of living Nuclei. 571 



nient and this was diluted to the desired degree. For most purposes a 

 Solution of from -002^ to -001 % was found best, but in a few cases weaker 

 Solutions gave better results, while in others it was found that staining di- 

 rectly on the slide, using a small amount of a much strenger Solution, was 

 preferable. 



The object to be examined is placed in this Solution and allowed to 

 remain until a satisfactory color is obtained. The time necessary for this 

 is extremely variable; with the root-hairs of Tradescantia zebrina, for ex- 

 ample, an immersion of less than half a minute in a «002 ^ Solution of 

 any of the three colors given, is sufficient — indeed a longer submersion 

 is generally fatal ; on the other hand, where the cell is protected by a thick 

 membrane as is the case with most aerial hairs, the cells may remain in 

 some cases for twenty four hours or more, and then in a great majority of 

 cases remain unstained. 



More or less successful coloring was obtained with the following plants. 



Nitella flexilis L., Chara sp., several undetermined Fern prothallia, 

 Lilium bulhiferum L., Lüium candidum L., Asphodelus albus Nees., Scilla 

 sp., Tradescantia Virginica L., Tradescantia rosea Mchx., Tradescantia ze- 

 brina, Sagittaria sagittifoliaL., Alisma plantagoL., Vallisneria spiralis L., 

 Elodea Canadensis Rieh., Trianea Bogotensis Karst., Hyoscyamus nigerL., 

 Campanula latifolia L. , Campanula rotundifolia L., Adenophora latifolia 

 Fisch., Cucurbita pepo L. 



The greater part of the time was devoted to the study of the stamen- 

 hairs of Tradescantia, as these proved to be the most convenient and satis- 

 factory subject for the demonstration of the nuclear staining. Of the species 

 examined T. Virginica was the best, but good results were also obtained 

 with T. ciliata and T. rosea ; with the first two species not only were the 

 resting nuclei stained, but the dividing ones as well. 



Tradescantia Virginica L. 



This well-known plant has been long a favorite one for the demon- 

 stration of protoplasmic Streaming which is particularly well marked in the 

 cells of the purple hairs at the bases of the filaments. The nuclei of these 

 cells are large and distinct and if young examples are selected the division 

 of the nucleus can be readily followed in life, as was shown by Stras- 

 burger 1). For demonstrating the staining of the nucleus young hairs should 

 be chosen as not only is the absorption of the color more rapid, but the 

 cell-sap in these is colorless where as in the older ones there is developed 

 an intense violet-purple pigment. 



In preparing the raalerial young buds are taken and the floral enve- 

 lopes carefully removed so as to expose the stamens which are allowed to 



4) Zellbildung und Zelltheilung. 3. Edit. p. 109. 



