578 Douglas H. Campbell. 



The cells take up the color slowly ; with a -001 ^ Solution of mauvein, 

 after four hours Immersion some of the large mesophyll cells had the nu- 

 cleus well colored, other experiments gave negative results. 



When the staining was done upon the slide, it was found that the ab- 

 sorption of the color was relatively slow even when streng Solutions were 

 used. Adropof -.1^ dahlia or methyl-violet, was run under the cover- 

 glass and allowed to remain for half an hour without killing many of the 

 cells. Some of the nuclei were pretty well colored after 10 or 15 minutes; 

 others remained completely unstained. 



Elodea Canadensis Rieh. 



This plant acts much like Vallisneria, the color being absorbed with 

 difficulty and the staining of the nucleus is uncertain. 



Trianea Bogotensis Karst. 



The mesophyll of the leaves of this aquatic plant contains large air- 

 chambers separated by thin plates composed of a single layer of cells. In 

 these cells the protoplasm circulates somewhat as in Vallisneria^ and Elodea, 

 but the nucleus is not so distinct and although a faint color could usuaUy 

 be obtained with the coloring agents used, the results were not entirely 

 satisfactory. 



Thin vertical sections of the leaf were mounted in water. A drop of 

 •1 % methyl-violet in a few minutes produced a slight nuclear stain, but the 

 cell-walls were also somewhat colored and there was formed a more or less 

 abundant precipitate in the cell-sap. 



With dahlia the results were mueh the same, but the color of the nu- 

 cleus was somewhat better and the precipitate less abundant. Further trials 

 with dahlia, using less of the Solution and allowing it to act for a very short 

 time, a minute or less, gave faint but unmistakeable nuclear coloring, violet 

 rather than blue, and at first no precipitate ; but after Standing for a short 

 time a slight precipitate appeared. When the action of the staining fluid 

 was short and care was taken to wash the preparation well, the circulation 

 was but Utile diminished. 



With mauvein the precipitate was much more abundant, and the nu- 

 clear coloring scarcely perceptible. 



When the sections were allowed to remain in a weak Solution for from 

 one to three hours, the results were the same — an abundant precipitate in 

 the cell sap and very uncertain nuclear colors. 



The root-hairs of Trianea were repeatedly studied, but owing to the 

 unfavorable position of the nucleus, which lies at the base of the hair sur- 

 rounded by abundant protoplasm, the staining is difficult to demonstrate. 



With very dilute Solutions of all three colors the nucleus in many cases 

 appeared to be certainly stained, but in order to see it clearly, longitudinal 



