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With Watery JEosin the stoppers are coloured a bright and 

 permanent pink ; Hcematoocylin also stains them bright rod. 



Iodine dissolved in potassium iodide gives a rich brown colour, 

 similar to that given by Eussow's reagent. Schulze's solution 

 also colours brown and without swelling the stoppers. 



Corallin-Soda stains beautifully, but, as is the case with ordi- 

 nary callus, the colour soon fades, and after a time disappears 

 entirely. 



Sands 9 s Picric Blue. — This is the aniline blue referred to in my 

 memoir on Protoplasmic Continuity. It is an admirable reagent 

 for callus, which it stains a peculiar blue, a blue much lighter 

 than that taken by protoplasm. Curiously enough, the stoppers 

 scarcely ever show any sign of blueing. A slight local stain 

 may occasionally be seen upon them, but this is probably due to 

 the protoplasm of the cell: from the reagent in question, the 

 stoppers take up picric acid alone, becoming yellow in conse- 

 quence. 



On running over the list of reactions, the resemblance in most 



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callus will at once be realized, and this is further emphasized by 

 resemblance in optical properties, both substances being iso- 

 tropic. The chief differences are : 



1. Insolubility of the stoppers in strong hydric sulphate. 



2. The rich brown with iodine. 



3. Eefusal to take up aniline blue. 

 Of these, the first is obviously immaterial in its bearing upon 



the proteid nature of the stoppers ; the second being a distinctive 

 proteid reaction, is an argument in favour of the proteid nature. 



tal to take up aniline blue is certainly a peculiarity, but I 

 think that when all the evidence in favour of the proteid nature 

 has been marshalled, this solitary reaction will be regarded as o 

 no effect upon the question. 



Eefu 



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Action of a Peptonizing Fluid upon the Stoppebs. 



* 



To determine this point, experiments were made in the way 

 already detailed when treating of the Vegetable-Marrow. A re- 

 markable difference in respect of gastric digestion between the 

 stoppers and Vegetable-Marrow callus soon came to light; tor 

 instead of gradually dwindling away and finally disappearing, 

 the stoppers gave no sign of the presence of a digestive fluid, 







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