36 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



for n hours, it will decrease in density, and it will lose, for example, m grams of starch- 

 substance which is dissolved by the ferment. If a new layer is now formed, it will be the 

 most dense. If the starch-grain is again exposed n hours to ferment action, the first layer 

 loses 2m gi'ams of substance, and the last-formed layer, that is, the second layer, loses m 

 grams by solution. 



Meyer states that there is present a second kind of solution, a corrosion of starch, 

 which occurs in the living cell. In and on the chlorophyl-grains solution of the starch-grains 

 takes place if the assimilation of the plants becomes sufficiently low. Starch-grains in 

 non-green cells are also dissolved on the exterior while they are still attached to the starch- 

 builder or leucoplast. Grains which are slowly dissolved from without take on a corroded 

 appearance, owing to a loss of some of thek substance, and during the action of the fer- 

 ment they are surrounded by a layer of less dense substance. The thickness of this layer 

 depends upon the length of time the ferment acts and upon the degree of activity of the 

 ferment. This outer corroded layer remains visible even after new starch is deposited. 

 Such a deposition on corroded grains takes place in both chloroplasts and leucoplasts, and 

 relatively thick layers originate which may be designated secondary layers in contrast 

 with the primary layers produced by the previously described change of conditions of 

 crystallization. 



In another article which appeared at about the same time (Botanische Zeit., 1881, 

 XXXIX, 856) Meyer reports the results of studies of starch-formation in the rhizomes of 

 Iris germanica and Iris pallida. The mature grains are described as oval, cylindrical, or 

 spherical, and as showing great diversity of forms and with an eccentric hilum. Usually 

 the grains in the cells nearest the tip of the rhizome are faintly lamellated, but very often 

 closed layers are entirely wanting. In parts of the one-year-old rhizome back from the 

 tips, grains are found, of approximately equal size, in which the closed layers are more 

 prominent than in the tips. The increase in the distinctness of lamellation he explains 

 upon the assumption that there is a solvent action on the starch in the cells. The grains 

 show conical lamellation, and the outlines of the layers which become visible through 

 ferment action are similar to those of the young stages of the grains of the rhizome tips. 



Meyer confesses his inability to determine whether the relatively low density of the 

 bases of the successive closed layers has arisen by the contact with the starch-builder and 

 the rapid supply of materia.1, or whether it is a form of lamellation determined by the 

 ferment, or whether it is due to both. It seems certain, however, he states, that the ferment 

 action emphasizes conical lamellation. In older parts of the rhizomes cells are sometimes 

 found filled with starch, but in others they are entirely starch-free. In going from such 

 old (mostly non-starch-bearing) parts toward the tip of the rhizome, starch-builders are 

 found which bear starch-grains; but these grains are mostly attached obliquely to the 

 builders, the grains having moved somewhat, so that now the original bases do not come in 

 contact with the builders. The grains are usually more or less corroded, and commonly 

 the side of the grain in contact with the builder is "eaten out." In parts of the rhizome 

 where the most active solution of the starch takes place, it is found in the autumn that 

 there are grains which have secondary lamellation. The presence of such lamellae in grains 

 that are usually attached diagonally to the builder supports the theory that in such parts 

 of the rliizome periodic solution and formation of starch-substance take place in the same 

 starch-builder. Since starch-builders have until their death the capacity to produce starch, 

 new grains may be formed or, if corroded grains are present, such grains may take on sec- 

 ondary lamellation; but the new grains are distinguished by their almost regular round 

 form and by their prominent radial striations, which are developed when the grains are 

 swollen in potassium hydroxide. The theory of the growth of starch-grains by apposition 

 furnishes, he states, a simple explanation of all of the phenomena observed in the devel- 

 opment of the starch-grains of the Iris rhizome. 



