178 KRAEMER — CONTINUITY OF PROTOPLASM. [April 4, 



grain. In the case of Nux vomica, solutions of potassium iodide 

 and iodine produce yellowish-brown striae in fresh sections (Fig. 

 13), closely resembling in form those produced by aniline stains 

 (Fig. 14), and which were considered by Tangl as being protoplas- 

 mic threads, but which are probably due to the precipitation of an 

 alkaloidal salt in the clefts or fissures in the wall.^ 



(4) The two kinds of layers behave differently toward chlor- 

 zinc-iodide ; the one next to the middle lamella and those alter- 

 nating with it are colored blue, while the others are but slightly 

 affected. 



The observations and comparisons herewith presented lead to 

 the following interpretations : 



(i) The starch grain, as also the cell wall, is made up of alter- 

 nate lamellae of colloidal and crystalloidal substances. 



(2) Physically, the structure of the starch grain and cell wall are 

 quite similar, although chemically different ; the preponderating 

 substance in the starch grain being granulose, while in the cell wall 

 the fundamental substance is cellulose, which may preponderate or 

 €xist in varying proportions. 



(3) The crystalloidal layer in the starch grain, consisting chiefly 

 of granulose, is colored blue with iodine or chlor-zinc-iodide, 

 whereas in the cell wall this layer, consisting chiefly of cellulose, 

 is colored blue only with chlor-zinc-iodide. 



(4) The colloidal layers in both the starch grain and cell wall 

 take up and hold various aniline dyes, the layers being, however, 

 more clearly defined in the starch grain, particularly potato starch. 



(5) In starch grains as in cell walls, there are radial clefts or 

 colloidal areas which under certain conditions also take up and 

 hold various aniline stains. 



(6) The plastid at the periphery of the starch grain may be 

 compared to the protoplasm of the plant cell, each contributing to 

 the growth of successive new layers. In the cell wall the mode of 

 growth is centripetal, whereas in the starch grain it is centrifugal. 



The peculiar bi-convex arrangement of the groups of striae be- 

 tween contiguous cells in the Nux vomica and vegetable ivory is 

 rather suggestive of fundamental lines of development corresponding 

 to chromatin threads, although they may be modifications of the wall 



^ This may explain why the iodine method alone has not met with any success 

 save in the case of fresh sections of Nux vomica. 



