444 



STARCHES OF AROIDE^ 



I GV T P 

 S 



Chart No. 78. 



G V 5 T CI CA PA FC P 3 Cl_P_A CA 



Curve of Reaction-Intensities of Starch of 

 Arum italicum. 



The lamellce are indistinct; only some near the hilum are visible. They are coarse, regular, 

 concentric rings, invisible in many grains. 



The grains vary in size from 2 to l(j/i. The common size is 10^. 



Polariscopic Properties. The figure is usually clean-cut, in the form of a cross; generallj' very 

 slightly eccentric. The lines are broad antl straight, tending to widen centrifugally. 



The degree of polarization is fair, varying somewhat in different grains, being higher in the 

 larger grains, and about the same in different aspects of the grains. It is higher than in A. palcestinum. 



With sclenile the quadrants are well defined, com- 

 monly regular in shape, and, as a rule, about equal in size. 

 The colors are fairly pure. 



Iodine Reactions. With 0.25 per cent Lugol's solu- 

 tion the grains color deeplj' a blue-violet. The depth of 

 color is about the same as that of the grains of Arum 

 palcestinum. Using 0.125 per cent solution the grains are 

 colored lightly at first, the tint soon deepening, the reac- 

 tion lieing the same as that oi A. pakvstinum. After heat- 

 ing until all the grains are completely gelatinized, the 

 solution is colored deeply, but the grains not very deeply, 

 upon the addition of iodine. After boiling for 2 minutes 

 the solution is colored more deeply, the grain-residues 

 faintly. All of the capsules contain some blue-reacting 

 starch, and it is therefore often difficult to demonstrate 

 the reaction of the capsule, but capsules devoid of blue- 

 reacting starch become of a violet color with an excess 

 of iodine. 



Staining Reactions. W\th gentian wofei the grains be- 

 gin to stain lightly in 2 to 3 minutes, and after 30 min- 

 utes they are not much more stained. The color is the same as that in the grains of A. palcestinum. 



With safranin the grains begin to stain very lightly in 30 seconds to a minute, but after 30 

 minutes the color has not deepened. The stain is lighter tlian that of A. palcestinum. 



Temperature Reaction. The temperature of gelatinization is 71 to 73 C, mean 72. 



Ejfects of Various Reagents. With chloral hyclrate-iodirie reaction begins in many grains in 

 30 to GO seconds. About half are darkened in 5 minutes, all but a few in 15 minutes, and the reaction 

 is over in practically all in 27 minutes. The hilum becomes more prominent, the edges and corners 

 of the facets begin to darken and swell, the rest of the margin grows darker, and the process spreads 

 inward over the whole grain. There is not much swelling connected with this reaction, and the 

 line of demarcation between the swollen and unswollen portions is not marked. The gelatinized 

 grains often sliow a central light space surrounded by a dark ring, and as they are not much swollen 

 they retain much of the original form of the grain. 



The reaction with chromic acid l>egins immediately and is over in 4 to 5 minutes. The hilum is 

 not very prominent and it jirotrudes. The grain becomes divided by striae which soon are enlarged into 

 coarse fissures. The central, less resistant starch is changed into a gelatinous mass, and the outer, 

 more resistant portion forms a ring at the margin, which at first is thick and coarsely striated, but later 

 becomes thin and transparent. The ring or capsule dissolves at the proximal end, the contents pass 

 out and are dissolved, and the capsule undergoes solution, the distal end being the last to disappear. 



With pyrogallic acid there is a general reaction in 30 seconds. Most grains are gelatinized in 

 5 minutes and all in 7 minutes. The hilum becomes very prominent and then begins to swell. 

 The grain is divided by fine strise, and the less resistant portions pass into a gelatinous mass as the 

 grain swells. The more resistant starch forms a finely striated ring at the margin, which ring becomes 

 thinner and clearer as the grain swells. The gelatinized grains are fairly large and smooth and 

 retain much of the original shape of the grain. 



The reaction with ferric chloride begins in some grains in a minute; most are gelatinized in 5 

 minutes and all in 10 minutes. The reaction consists in the gelatinization and swelling of the less 

 resistant central ]iortion and the gathering of the more refractive ]^orti(jns at the margin in a more 

 or less homogeneous ring. This ring grows thinner and transj^arent as gelatinization proceeds. 

 The gelatinized grains are large and smooth and retain much of the original form of the grain. 



