STAKCH PROTEIN 249 



Stai'ch turns blue with iodine (75). The color may be 

 driven away by heat, but will return again as the tempera- 

 ture lowers. To test for starch: .Make pastes with wheat 

 flour, potato starch, and corn starch. Treal a little of each 

 with a solution of rather dilute iodine. Try grains from 

 crushed rice with the same solution. Are they the same 

 color.' Cut a thin section from a potato, treat with iodine 

 and examine under the microscope. To study starch 

 (/ruins: Mount in cold water a few grains of starch Prom 

 each of the following: potato, wheat, arrow-root (buy 

 at drug store), rice, oats, corn, euphorbia. Studj the sizes, 

 forms, layers, fissures, and location of nuclei, and make a 

 drawing of a few grains of each. 



402. Amylo-dextrine is a solid product of the cell 

 much resembling starch in structure, appearance, and use. 



With the iodine-test the grains change to a \\ i red color. 



Seeds of rice, sorghum, wild rice, and other plants contain 

 amylo-dextrine. A.mylo- dextrine is a balf-way stage in 

 the conversion of starch into maltose and dextrine. These 

 latter substances do not read with iodine. 



(ii.;. Protein or uitrogenous matter occurs largely in 

 the form dt' aleurone grains, and is mosl abundant in 

 seeds of various kind- The grains are very -mall, color- 

 lessor yellowish in mosi plants, rarelj red or green. In 



the common cereals thej npj the outer 



layer of cells of the endosperm. Pig. 392. 

 In many other eases thej an 1 distributed 

 throughout the Beed. The grains \ arj in 

 size and form in diil'ep-nt species, iui 



are rather constant within each group. 



.... i iii- i 



Thej are ent irelj Boluble in water uul< 



certain hard part- or bodies, known as inclusions, are 

 present, and these maj remain undissolved. The in- 

 clusions raaj be {a) crustaloids, as in potato, castor ml 

 aeed; (6) globoids, as in peach, mustard ; (r) calcium 



