MICRO-CHEMISTRY OF THE CELL. 33 



II. The CELL CONTENTS. 

 a. The Protoplasm. 



i. Coloured yellow by iodine, and by Schulze's solution. 



ii. Coloured yellow by nitric acid, the colour becoming 

 more intense on warming ; on the addition of potash or 

 ammonia a bright yellow colour is produced (xantho- 

 proteic reaction). 



iii. Coloured violet after treatment with dilute solu- 

 tion of copper sulphate on the addition of potash. 

 Fehling's solution may be used. See page 20. 



iv. Coloured pink after treatment with syrup on the 

 addition of dilute sulphuric acid. 



v. Stains readily with solutions of carmine, hgema- 

 toxylin, and Hoffmann's blue ; bright red with Hanstein's 

 aniline violet. 



These reactions are given by all bodies consisting of proteids. 



I. The Chlorophyll-corpuscles. 



On treatment with alcohol the green colouring- 

 matter (chlorophyll) is dissolved, and the substance of 

 the corpuscle is left: this gives the reactions enu- 

 merated above as being characteristic of proteids. 



The orange colour of many fruits and flowers is due to the 

 presence of coloured granules which appear to be modified 

 chlorophyll-corpuscles (chromoplastids). These may be well 

 observed in the petals of Tropceolum. 



c. The Starch-grains. 



Coloured blue on treatment with iodine. 

 Coloured pink with corallin solution (p. 12). 



In order to detect the presence of minute starch-grains in 

 chlorophyll-corpuscles, the tissue must be kept in alcohol exposed 



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