STARCH-SUBSTANCE, AND THE STRUCTURE, ETC., OF THE STARCH-GRAIN. 27 



starch, maranta starch, etc., in a little water, when the beginning of solution is soon noted, 

 for the entire mass becomes viscous and mucilaginous. On the addition of more water 

 a clear solution is obtained, on whose surface float torn and broken "integuments" of 

 the starch-grains, while the unbroken grains sink to the bottom. The filtrate shows no 

 precipitate, but becomes blue with iodine. Jessen agrees with Harting (page 23) that the 

 starch-grain has a structure like that of cells, and that the concentric lines on the grains 

 are cell-walls or condensed layers between wloich the soluble starch is deposited. In a 

 later research (page 29) Jessen records that starch consists of three substances : the integ- 

 uments, starch soluble in cold water, and starch insoluble in cold water. 



Wicke (Ann. d. Physik u. Chem. 1859, cviii, 359) holds, in opposition to many previ- 

 ous observers, that pulverized starch-granules are almost entirely insoluble in cold water, 

 only very small portions going into solution. 



The statement of Nageli that the cellulose of the starch-grain remains as a residue 

 after the solution of the granulose seemed to von Mohl (Botanische Zeit., 1859, xvii, 225) 

 to be not well-founded. Von Mohl therefore undertook a series of experiments to prove 

 or disprove this point. He used chiefly the starch from the rhizome of Carina indica, and 

 for the extraction of the substance (granulose) which was colored blue with iodine, he 

 utilized saliva. At a temperature of 35 to 40 C. the extraction of the .soluble substance 

 began slowly, and proceeded regularly from the periphery of the grain to the center. At a 

 temperature of 50 to 55 the extraction was completed in several hours. An exainination 

 of the grains from which the soluble constitutents had been thus removed showed that they 

 had lost in weight; that they float more readily in water; that they are less refractive to 

 light; and that they are smaller, but just how much was difficult to determine. The 1am- 

 ellation underwent no change, except that in many cases, as in sprouting wheat, it became 

 more evident during the process of solution. The grains from which the soluble matter had 

 been extracted by saliva behaved exactly towards polarized light as do unchanged grains. 



Von Molil opposes Nageli's statement that granulose and cellulose can be differentiated 

 by iodine. He states that whether iodine produces a red or a blue color depends neither on 

 the fact that the object stained may be starch (granulose) or cellulose, nor on the amount of 

 iodine present, but essentially on the behavior of the organic substance toward water. If 

 a small amount of water is absorbed a red coloration ensues; if a larger amount, there is 

 a blue coloration. One can produce, he states, a beautiful blue in cellulose, and a red or 

 violet in starch (granulose) without bringing about a chemical change in the objects colored, 

 the coloring being regulated by the amount of water absorbed. It is therefore clear, he 

 holds, that the blue coloration of cellulose with iodine is in no wise proof that the cellulose 

 is changed wholly or partly into starch; and, moreover, that iodine furnishes no means 

 whatever of differentiating granulose from cellulose. 



Furthermore, von Molil holds it can be demonstrated, from both physical and chemical 

 standpoints, that the substance (cellulose) remaining in starch-grains after treating the 

 grains with saliva is not identical with the cellulose of plants. The so-called cellulose of 

 the starch-grain, he states, is very brittle, while plant cellulose is tenacious to a remarkable 

 degree. The effects of polarized light on the two are opposite. Caustic potash dissolves 

 starch cellulose instantly, but swells up plant cellulose, and dissolves it only after a num- 

 ber of hours. In nitric acid and muriatic acid starch-grains are dissolved at once, but 

 plant cellulose is dissolved only by boiling. Other chemical reagents showed similar con- 

 trasts in their effects on the two substances. Von Mohl proposes the name farinose as a 

 substitute for the term cellulose of Nageli. 



The nature of the substance of raw starch that is soluble in cold water was also 

 examined by Delffs (Aim. d. Physik u. Chemie, 1860, civ, 648), who macerated com- 

 minuted starch-grains in water for 24 hours, after which a clear liquid was filtered off 

 which gave a blue reaction with iodine. The soluble constituent he regards as being a 



