CALYCIN CAROTIN 339 



in a saturated solution of sodium carbonate. After remaining 

 in this solution for a time, the sections should be examined 

 in glycerine. If the sections are overstained, the intensity of 

 the stain may be reduced in a 4 per cent, solution of sodium 

 carbonate. The aniline blue should be used in dilute aqueous 

 solutions, in which the sections are to remain for about half 

 an hour. Overstaining may be remedied by washing out in 

 glycerine. 



Calycin, C 18 H 12 O 5 . This occurs in the tissues of many 

 lichens. Its presence may be demonstrated by moistening 

 some of the powdered lichen with glacial acetic acid, and when 

 the preparation dries, the long, doubly refractive crystals of 

 calycin are deposited. When a section of lichen containing 

 calycin is treated on the slide with a few drops of chloroform 

 and a drop of sodium hydrate, that portion of the section which 

 contains calycin assumes a color varying from brick-red to 

 blue-red. 



Cane-sugar (Sucrose), C 12 H 22 O ir This carbohydrate is 

 of common occurrence in plant tissues. At 15 C. it is soluble 

 in part of water. It is difficultly soluble in alcohol. When 

 boiled with Fehling's solution, it does not at first precipitate 

 cuprous oxide, but on longer boiling it becomes converted 

 into glucose and laevulose, which are capable of reducing Fehling's 

 solution. If rather thick sections containing cane-sugar (the 

 sugar-beet affords good material) are placed for a short time in 

 a concentrated solution of cupric sulphate, and then quickly 

 rinsed in water, transferred to a solution of i part of potassium 

 hydrate in i part of water, and heated to boiling, the cells con- 

 taining the sugar take on a sky-blue color. A blue color is also 

 produced by Fehling's solution when sections containing cane- 

 sugar are heated in a drop of the solution on a slide until bubbles 

 arise. 



Carotin, C 26 H 38 . Carotin occurs in the orange and red 

 chromatophores of many flowers and fruits, and, indeed, most 

 orange and red colors of both plants and animals seem to belong 

 to the carotins; carotin seems also to be an essential part of 



