562 ELEMENTS OF PLANT HISTOLOGY AND MICROTECHNIC 



or not at all by the iodine. The solution of potassium hydrate at ordinary tempera- 

 tures affects the crystals so that they are colored blue by the iodine after the solu- 

 tion has been neutralized with acetic acid. In boiling potassium hydrate the crys- 

 tals are changed into viscid drops. If the solution is now neutralized with acetic 

 acid and diluted with four times its bulk of water, it takes on a deep blue color with 

 the iodine reagent. 



If a drop of malt extract is added to the solution formed by boiling crystals of 

 a-amylose with the potassium hydrate solution, and exactly neutralizing with 

 acetic acid, it is found after 5 minutes that the solution takes on a red color, due 

 to the formation of amylodextrine by the influence of the malt extract. Saliva and 

 malt extract have very little effect upon a-amylose. After treatment with these 

 reagents for 15 days at a constant temperature of 4OC., no essential change could 

 be detected. 



/3-Amylose is insoluble in cold water, but at a temperature of 7OC. it forms 

 viscid masses or minute droplets. The solutions of calcium nitrate, potassium 

 hydrate, and hydrochloric acid have the same effect as water, excepting that the 

 solution in hydrochloric acid is more complete than in water. The solution of 

 /S-amylose acts precisely as the solution of a-amylose. Undissolved /3-amylose, 

 however, is colored blue by the iodine solution. The swelling of starch in hot water 

 is probably due to the 0-amylose which it contains. Meyer considers a-amylose 

 and /3-amylose to be the same substance, but that the latter contains water of 

 crystallization, while the former does not. 



Anthochlorin. A yellow coloring matter dissolved in the cell-sap of flowers, 

 and differing from the yellow coloring matter xanthin occurring in chromoplasts in 

 that it is not changed to a blue color by the action of concentrated sulphuric 

 acid. 



Anthocyanins. These are coloring matters of flowers which impart red, violet, 

 blue, blue-green, or green colors, the character of the color being dependent on the 

 alkalinity or acidity of the cell-sap. The anthocyanins are soluble in water, 

 alcohol and ether, and are decolorized in strong alkalies. 



Anthoxanthin. This yellow coloring matter in the chromoplasts of flowers 

 and fruits takes on a blue color with concentrated sulphuric acid. Since the 

 chromoplasts of flowers and fruits were first of all green, anthoxanthin is probably 

 a derivative of chlorophyll. Anthoxanthin is also called xanthin and xanthophyll. 



Arabin. This is the gum derived from species of Acacia and known as gum 

 arabic. Arabin is soluble in hot and cold water, and insoluble in alcohol and ether. 

 The aqueous solution will mix with glycerine, but concentrated glycerine has little 

 effect on hard gum. 



Asparagin, C 2 H 3 NHj.CONHj.COOH. This is a nitrogenous compound of 

 simpler constitution that that of proteids. It is formed within plants both analytic- 

 ally by the decomposition of proteid, and synthetically probably by the combina- 

 tion of ammonia with formic aldehyde. Asparagin is soluble in water and in the 

 cell-sap, and is one of the most important nitrogenous compounds which are capable 

 of solution and circulation within the plants. It combines with non-nitrogenous 

 compounds to form proteids, and is apt to accumulate in those parts of plants where 

 there is not sufficient non-nitrogenous material at hand for the formation of 

 proteids. The accumulation of asparagin is particularly apt to occur in plants 

 which are grown in the dark, so that carbon assimilation does not take place. 

 Thus, Pfeffer found that when seedlings of lupin were grown in the dark, they con- 

 tained a large amount of asparagin, but when they were brought to the light, the 

 asparagin disappeared. He found that this was not due simply to the influence 

 of the light, for when the seedlings were exposed to the light in an atmosphere 

 destitute of carbon dioxide, the asparagin persisted in the seedlings. For the 



