426 M. H. V. Mohl on the Structure of Chlorophyll, 



grains are formed both in chlorophyll and in colourless proto- 

 plasmic masses, I am inclined to regard it as a product formed by- 

 deposit or secretion on the inside of cavities or vacuoles of the 

 latter, by a process analogous to the formation of the cellulose 

 layers on the outside of the primordial utricle*. I do not find 

 the protoplasmic nucleus described by Cruger in all starch- 

 grains. This would account for most of the phsenomena observed. 

 At the same time it would afford an argument for those who 

 doubt the distinct existence of a determinate layer or primor- 

 dial utricle on the outside of the protoplasm. Our author's state- 

 ments as to the pellicular character of the apparent membrane 

 described by Nageli on starch and chlorophyll-corpuscles, would 

 seem to apply to some extent to the so-called primordial utricle, 

 Pringsheim has recently published some important observations 

 on this head, which I trust to be able shortly to test and report 

 on in this Journal. — A. H.] 



* [The observations of Mr. Grundy (see ante, p. 386 of this volume) 

 agree in some respects with those I have made in a great variety of cases, 

 but the striae are certainly not superficial, and I doubt the existence of the 

 outer membrane. I think there is merely a pellicle of protoplasm, coagu- 

 lated on the starch-grain when reagents are added. This would appear to 

 dip between the constituent grains of groups ; in some cases, however, the 

 interposed pelUcle becomes obliterated, and the groups, mostly j^airs in such 

 cases, have the outer layers common over the whole. It seems to me that 

 there is a fallacy in the various accounts of the membrane of the starch- 

 granule, founded on the experiment of boiling starch, assuming as I do, 

 after repeated experiments, that the main body of the structure is that 

 of concentric laminae of a tough material. If there were an enclosing 

 membrane distinct from the starch-layers, thick enough to bear expanding 

 to many hundred times its original superficial dimensions, this must be 

 thick enough when unexpanded to be clearly visible as a well-defined coat. 

 The saccate bodies obtained by boiling really result from the whole softened 

 substance of the granules becoming blown out (like india-rubber bottles) by 

 a process of endosmosis. The internal substance softens and absorbs water 

 more readily than the outer, — a sufficient cause for the endosmosis. This 

 difference of condition of the layers is proved by an experiment I have re- 

 peatedly made with fresh potato-starch. If we attempt to cut it with a 

 knife, it breaks with a roughish fracture, like a lump of partially hard- 

 ened clay ; if the fragments are placed in cold water, the internal part of 

 the starch will often swell and protrude irregularly, while the outer layers 

 retain their shape. I cannot confirm Mr. Grundy's statement, that the 

 " skins " can be boiled until they no longer take the blue (or bluish) 

 colour with starch. Still, since after boiling, as in treatment with sulphuric 

 acid, the colour of the substance with iodine tends more and more to pinkish 

 purple, it is possible that long boiling may change the condition, just as 

 roasting does. — A. H.] 



