STARCH-SUBSTANCE, AND THE STRUCTURE, ETC., OF THE STARCH-GRATN. 31 



and that such chlorophyl-grains may produce six or more starch-grains. Starch-grains which 

 arc produced within the chlorophyl-grain, and remain surrounded by it, attain a concentric 

 structure, and most grains originating in this way remain very small and without definite 

 structure. In Vanilla plamfolia the mature starch-grains consist of hundreds of colorless, 

 polyhedral granules of equal size, which originate as very small points in the clilorophyl, 

 and become larger, and at the same time polyhedral through mutual pressure. Starch- 

 grains which develop at the periphery of the chlorophyl-grain show a differentiation into 

 hila and lamelliT'. Such grains are always eccentric, and the growing side of each grain is 

 that to which the chlorophyl-grain is attached. 



It is obvious, Schimper states, that the unequal growth on opposite sides of the hilum 

 is the result of unequal "nourishment." Such a conclusion, he finds, is supported by the 

 fact that where starch-grains are partly in contact with chlorophyl-grains they become 

 gibbous at the points of contact. Starch-grains developing in flat chlorophyl-grains are 

 wedge-shaped at first, being flattened in the same manner as the chlorophyl-grains. W^iere 

 starch is produced very actively, the chlorophyl-grain assumes an isodiametric form, 

 decreases in density and later in size, until finally it is present as a mere remnant, while at 

 the same time the starch-grain becomes denser and assumes an oval shape. With the dis- 

 appearance of the chlorophyl the growth of the starch-grain ceases. In chlorojihyl-grains 

 capable of producing starch-grains within their entire mass, the starch-grains may appear 

 near the surface of the chlorophyl, and later on break through. Such grains are eccentric. 



Scliimper's examination of non-green starch-bearing plants showed that starch-grains 

 are not surrounded by ordinary protoplasm, but are inclosed by or attached to refractive, 

 spherical, or spindle-shaped bodies which are but little affected by alcohol and are rather 

 unstable. A study of the youngest stages of these bodies (later designated leucoplasts) 

 demonstrated their presence before starch-grains are formed and that the starch-grains, at 

 their appearance and during their development, indicate similar relations to these bodies 

 as are borne by other starch-grains to chlorophyl granules. The starch formed in these 

 albuiuinous-hke bodies has an eccentric structure like the eccentric grains produced by 

 chlorophyl-grains, and the entire behavior of these bodies is like that of chlorophyl-grains, 

 and therefore they are starch-builders. Schimper then gives the mechanisms of formation 

 of starch by starch-builders in non-chlorophyllous plants and refers to the formation of 

 starch in roots as an instance of starch-building by these colorless bodies, or leucoplasts. 

 He also noted that in most cases the colorless starch-builders may, under the influence of 

 light, be transformed into chlorophyllous bodies. 



In the second and third communications Schimper (Botanische Zcit., 1881, xxxix, 

 185, 201) goes more in detail into the processes and stages of development of starch-grains 

 in different plants. He found that the grains growing in many chlorophyllous plants show 

 certain constant peculiarities. Tabular grains have irregular lobes and are laterally de- 

 pressed, and at times are porous; their broad surfaces are uneven and present a spotted 

 appearance, owing in part to surface structure and in part, in many cases, to internal 

 vacuoles. These phenomena he ascribes to partial solution, which occurs when starch 

 is used for the growth of the organ in which the starch-grains are formed, as in germinating 

 seeds of Zea mays. Even after the starch-bearing organs cease to grow, or slacken growth, 

 starch is formed. There may originate spherical structureless grains; or corroded grains 

 already present in the cells may take on new growth, which occurs in the form of a layer 

 around the corroded grain, thin at first, but gradually becoming thicker and more refrac- 

 tive. This layer shows the projections and depressions of the corroded grain. Layers 

 subsequently formed go through the same process, but the roughness of the surface becomes 

 less pronounced as new layers are deposited, so that the mature grain appears smooth; 

 but iDy suitable illumination the original corroded grain may be seen in the center of the 

 mature grain. 



