40 DIFFERENTIATION AND SPECIFICiri' OF STARCHES. 



laj'ers swell up and separate from one another. When the granules are heated more strongly 

 with a drop of water on the object glass, a deep-blue coloration ensues. The residue is 

 not a uniform body, but contains, in addition to cellulose and granulose, a transformation 

 product of starch, similar to dextrin, which reduces Fehling's solution, is colored red by 

 iodine, and undergoes decomposition on treatment with water. It could not be decided 

 whether or not this body was erythrodextrin. If a large quantity of the grains is triturated 

 with powdered glass, which presumably would not produce decomposition or alteration, 

 the substance yielding the red color can not be removed by repeated treatment with cold 

 water; on the contrary, by the addition of iodine the residue becomes more intensely 

 colored blue, while the rotatory power remains practically unaltered. 



The development of the starch-grain in the lactiferous cells of Eiiphorhiaccce, first 

 observed by Meyer in 1836, was studied by Potter (Jour. Linnean Society, 1884, xx, 446), 

 who describes phenomena of much interest. These grains are formed in the interior of 

 rod- or spindle-shaped corpuscles which lie in the parietal protoplasm of the cell. The 

 starch-grain is at first visible as a tliin streak in the interior of the corpuscle. Tliis streak, 

 through the deposition of starch, assumes a rod- or spindle-shape, and both grain and 

 corpuscle increase in size. When the grain has attained nearly its maximum dimensions 

 in length and breadth, the starch-forming corpuscle collects at both ends of the rod-sha]3ed 

 grain and forms masses at the ends which cause the former to assume a remarkable shape, 

 resembling a long bone, such as the tibia. The lactiferous cells are polynuclear, and since 

 when very young their diameter does not much exceed that of the nuclei, it follows that 

 the starch-forming corpuscles which are always formed near the nucleus must be developed 

 at the sides of it. The smallness of the diameter of the lactiferous cell necessitates the 

 starch-forming cell being much longer than broad, and hence it comes about that the 

 prunitive shape of the grain should be that of a rod. Later, however, when the cell has 

 increased in diameter, the rod can also increase in diameter. The hilum of these grains 

 is seen in the form of a line in the middle of the grain in the tlu-ection of its long axis. Tlie 

 lines of stratification inclose the hilum and are roughly parallel to the outline of the grain. 

 The grains are doubly refractive, and in all respects agree with starch-grains from other 

 sources, since they are developed in the interior of starch-forming corpuscles and are strati- 

 fied and rendered doubly refractive through the agency of the lamella?. 



The view that the starch-grain is composed, according to C. Niigeli, of granulose and 

 cellulose was opposed by De Vries (Botanische Jahresberichte, 1885, i, 122), who holds 

 that the so-called starch-skeleton does not consist of cellulose, because most or all of such 

 skeletons are colored blue by boiling in Lugol's solution. He believes that only one carbo- 

 hydrate (amylum or granulose) is present in the grains, that it may exist in different 

 degrees of density, and hence that the starch cellulose is merely a dense form of granulose. 



In the same year Mikosch (Botanische Jahresberichte, 1885, i, 122) reported the results 

 of his inquiries into the seat of origin of starch-grains. He placed leaves on a sugar solution, 

 and observed that starch-grains arise not only in chlorophyl grains, but also in any part 

 of the protoplasm. He found the same to take place in the potato tuber. In the cotyle- 

 donary leaves of Zea mays and in the young tissue of Elodca canadensis the grains were 

 observed to originate in the plasma of leucoplasts. 



At the same time an article by Belzung (Botanische Jahresberichte, 1885, i, 122) appeared 

 on the mechanism of the development of the starch-grain. He fomid in sprouts develoji- 

 ing in the dark that leucoplasts arise which soon after their appearance form several small 

 starch-grains. After a short period of growth the grains fill the leucoplasts, and finally the 

 grains in one leucoplast may fuse mto a single grain, or by atrophy of the leucoplast they 

 may lie free as small grains in the protoplasm. In general, he states, there are three methods 

 of development of starch-grains: (1) The formation of grains within the chromatoi:)hore by 

 "resorption," but without marked subsequent growth (seen in sprouts, leaves); (2) the for- 



