STARCH-SUBSTANCE, AND THE STRUCTURE, ETC., OP THE STARCH-GRAIN. 55 



appears homogeneous, dense, and sharply bounded. Hence tlie relations of the methods 

 of starch formation in H ijdrodidijon and in chromatophores witliout pyrenoids must be 

 regarded at present as uncertain. 



In a series of precipitation-staining experiments, Fischer (Beihefte z. bot. Centralbl. 

 1902, XII, 226) tried various aniline and other dyes, using picric acid as the precipitant 

 instead of calcium nitrate, which was employed by Meyer (page 51). Such grains were 

 found (1) to be unaffected by nigrosin, Hessian purple, diamond red, Kongo red, carmine, 

 aniline blue, and cyanin; (2) to be uniformly colored by acid fuchsin, corrallin, eosin, 

 crocein, tropa^olin, Martin's yellow, and hemotoxyhn; (3) to be in the form of fine pre- 

 cipitates by fuchsin, safranin, indigo carmine, methyl blue, methylen blue, and indulin; 

 (4) to give large crystalline grains by methyl violet and gentian violet; (5) and exhibit 

 radial needles by Bismarck brown, chrysodin, malachite green, brilliant green and thionin. 

 These precipitation-staining reactions were confined to the less dense layers. The outer 

 surface or layer was unaffected. 



Rraemer (Botanical Gazette, 1902, xxxiv, 341) conceives the starch-grain to be a 

 direct product of the polymerization of soluble carbohydrates of either the glucose or 

 cane-sugar group, and that during the processes of formation the products consist of three 

 substances, two crystalloidal in tlie form of starch-cellulose and granulose, and one colloidal. 

 These are assumed to occur as follows: (1) In the point of origin of growth (the hilum) 

 the colloidal substance is associated with a small proportion of cellulose, as also in the 

 alternate lamellae. (2) In the other layers occurs the granulose associated with a small 

 amount of colloidal substance, and possibly also some cellulose. (3) The peripheral layer 

 of the grain is not readily acted upon by reagents, and is quite elastic and more or less 

 porous, probably consisting of an anliydride of cellulose. (4) In some cases some of the 

 dextrins, or some of the non-colloidal or crystalline carbohydrates, such as maltose, dex- 

 trose, levulose, etc., may be present, probably formed as results of alterations taking place 

 in the grain. 



Certain aniline dyes were used by Kraemer to differentiate the lamella) of the starch- 

 grain. Freshly prepared starch-grains, or commercial starches, were treated with weak 

 aniline solutions of safranin and gentian violet and allowed to dry at ordinary temperature, 

 when it was observed that certain parts of the grain took up the stains more readily than 

 others. He also used iodine, water, and various other reagents for the same purpose, and 

 he makes the important observation that the grains from different plant sources do not 

 react the same. The gentian-violet stain was found to be more pronounced in its effect 

 upon potato starch than upon the starch of wheat and corn, the stain being held by the 

 point of origin of growth (the hilum) and by the lamellae alternating with it. On the other 

 hand, he ascertained that safranin is a better differential stain for wheat starch, being 

 held in certain of the lamellae (usually not more than tlu'ee or four of them being affected) 

 and also in numerous radial clefts and channels. Corn starch did not appear to take up 

 these stains as readily as either wheat starch or potato starch, and there was no differentia- 

 tion of lamellae, which Ki-aemer thinks as being probably due to the peripheral layers 

 being denser and less permeable. 



In referring to the previous work of Salter (Jalirbiicher f. wissensch. Bot., 1898, xxxii, 

 117), Kraemer takes exception to his statement that the dye has not a selective or spe- 

 cific action on the layers, and he states that Salter's figures show that certain parts of 

 the grain stain more than others, and that he believes Salter's work, as well as that of 

 Meyer {loc. cit.), with methyl violet, correspond with his own in that the layers that are 

 colloidal in character take up the stain. He notes that the lamellae which are not affected 

 by the aniline stains become blue with iodine, the alternate layers and the point of origin 

 of growth remaining luiaffected. The layers thus affected by iodine, he states, are the ones 

 that are rich in granulose and more clearly defined in the grains of potato and wheat starch 



