MORPHOLOGY OF HIGHER PLANTS. 165 



grains the lamellae are indistinct or wanting, as in wheat and corn 

 (Fig. 316, C,D). 



(6) Behavior toward dilute iodine solutions, the color pro- 

 duced varying from a deep blue in most starches to a red or yel- 

 lowish red, as in the amylodextrin grains of mace. 



(7) The temperature (45"-77" C.) at which the " kleister " 

 or paste is formed, and its consistency. 



(8) The appearance as viewed by polarized light, the dis- 

 tinctness of the cross, as well as the kinds of colors produced, 

 varying considerably as Nichol's prism is revolved (Fig. 95). 



(9) Behavior toward various reagents, as chromic acid, cal- 

 cium nitrate, chlor-zinc-iodide, diastase and various aniline stains, 

 peculiarities of both structure and composition being manifested 

 (Figs. 96 and 97). 



General Properties of Starch. — If starch is triturated with 

 water and the mixture filtered, the filtrate does not give a reaction 

 with iodine solution ; if, on the other hand, the starch is previously 

 triturated with sand and then with water, the filtrate becomes blue 

 on the addition of iodine solution. It appears that in the latter 

 operation the wall of the grain is broken and the soluble starch 

 present in the grain is liberated. 



If dry starch and iodine are triturated together no color or, 

 at the most, a faint blue color is produced; whereas, if a little 

 water is added and the trituration repeated, a deep blue color is 

 immediately produced. 



The blue color of starch solution and iodine disappears on the 

 application of heat, but slowly returns on cooling the solution, 

 but not with the same degree of intensity, part of the iodine 

 being volatilized. 



When starch is heated with glycerin it dissolves, and if alco- 

 hol is added to the solution, a granular precipitate is formed which 

 is soluble in water, the solution giving a blue reaction with iodine. 



When starch is heated with an excess of water at 100° C. for 

 varying periods of time, it completely dissolves with the forma- 

 tion, first, of soluble starch, which gives the characteristic blue 

 reaction with iodine ; then the production of dextrin compounds, 

 giving violet-red, reddish and yellowish reactions with iodine; 

 finally, maltose and dextrose are produced, these giving no reac- 



