42 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



states that the envelope of the starch-grain undoubtedly originates in the cytoplasm, as 

 is shown in the different stages of development observed in the various i^reparations. 

 The inclosed grains are stated to have an extraordinary similarity to the grains of the 

 seeds of Vicia narhonensis, with the difference that in Juncus the capsules usually have 

 stalks, while those of Vicia never have. 



The cause of the lamellation of the starch-grain is due, according to Zimmermann 

 (Beitriige z. Morph. u. Physiol, d. Pflanzenzelle, 1890; Botanical Microtechnique, Trans, 

 by Humphrey, 1893, 226), to varying water-content, which, according to the author, may 

 be shown by examining moist and cLry starch-grains in Canada balsam. He notes that 

 the complete removal of water can only be accomplished by drying at a temperature of 

 50 to 100 C, and that the use of dehydrating media, such as absolute alcohol, does not 

 give demonstrative results. 



In an investigation of the mechanism of the growth of starch-grains, Eberdt (Jahr- 

 biicher f. wissensch. Botanik, 1891, xxiii, 293) attempts the support of the then practically 

 abandoned theory of growth by intussusception, and among other things he holds very 

 different views from Schimper regarding the role of the colorless starch-builders, or leuco- 

 plasts. Eberdt contends that the starch-grains which originate in the interior of chlorophyl 

 granules become larger after they are freed from the granules, which to him indicates a 

 formation by concentric lamellation, a process that can only be explained by growth by in- 

 tussusception. The appearance of lamellation in starch-grains, he states, be it concentric 

 or eccentric, might be explained by a leaching-out process brought about by plant acids, 

 but the tensions present in the starch-grains would remain to be explained, and hence one 

 must at the same time assume that simultaneously with this process swelling takes place. 



Eberdt agrees with Schimper that in non-asshnilating plant parts the formation of 

 starch is due to albuminous bodies. Schimper ascribed an active role to these bodies, 

 looking upon them as starch-builders, but Eberdt believes that they are passive, and that 

 the plasma is the active agent in the transformation of assimilation products into starch. 

 Eberdt holds that during the life of the plant, when no reserve material is produced, these 

 albumin bodies perform no apparent function, and that one might in many cases regard 

 them as waste products ; but when reserve material is being formed the role played by them 

 is passive, and they become transformed into starch. Tliis transformation may be brought 

 about, he states, in two ways, either from within outward, as when the form of the starch 

 grain is analogous to the form of the body; or, the transformation takes place gradually 

 from without inward, in which case the body is completely dissolved, and the form of the 

 resulting starch-grain shows no resemblance to its form. In every case the transformation 

 is assumed to take place only in the presence and by the agency of protoplasmic substance, 

 which is the active factor, and which may become green under the influence of light. 



Eberdt gives a very lengthy discussion of the subject, but his chief conclusions may 

 be summarized as follows: (1) The origin of the small albuminous bodies (Stiirkekorner 

 of Schimper), which on account of their behavior he terms the "Stiirkegrundsubstanz," 

 result from a differentiation of the plasma of the cell. (2) These bodies may be attracted 

 to the cell nucleus, and later be arranged in groups or deposited singly about the nucleus. 

 In every instance they are surrounded by a layer of protoplasm which is connected with 

 the peripheral plasma of the cell by plasmic threads. (3) After the indi\'idual grains of 

 the groups have been transformed into starch, the plasmic layer completely surrounds 

 every group, or the layer breaks and the groups separate. In the former case the groups 

 are surrounded by the plasma until the starch-grains are mature, and the individual starch- 

 grains show no lamellation, or the grains separate before maturity, and in such cases con- 

 centric lamellae appear, and in some instances eccentric layers. Grains of the last two 

 types may increase in size after lying free in the cell-space. (4) In instances where the 

 bodies of the Stiirkegrundsubstanz are not grouped around the cell-nucleus, the plasmic 



