400 Prof. Hillhouse, Some Observations [May 28, 



experiments which I mainly carried on in the Botanical Institute 

 at Bonn. For this purpose I used dry old arrowroot starch. The 

 results of the investigation appear to be of some interest and 

 importance, as bearing on the physical constitution of the starch 

 grain, and the various theories of its growth. 



As my original investigation was undertaken in connection 

 with the presence of Tannin in the same cells with the starch 

 grains, I had allowed some of this dry arrowroot starch to lie 

 for a few days in a weak aqueous solution of tannin, and tested 

 these with the reagent, at the same time testing other grains 

 which I had merely damped with absolute alcohol. Some of 

 the slides thus treated happened to lie upon my table, and to be 

 examined the next day, when I was surprised to find that in 

 one of these preparations the starch grains were mostly swollen in 

 such a way as to preserve distinct lamination (see Fig. 8). Whether 

 the alcohol or tannin grains had so swollen I could not say, so I 

 repeated the experiments with numerous cases of both, carefully 

 watching the progress of the phenomena. It is unnecessary to 

 give details of these experiments, the results of which, especially 

 with the tannin specimens, varied considerably. I have therefore 

 collected into a succinct form the various facts observed. 



Grains which had lain lor three days in tannin 1 solution showed 

 very few signs of stratification. The nucleus (hilum) was rarely 

 visible, though its position was not infrequently indicated, as 

 with dry grains, by a dark cleft, — dark, from the presence of air 

 or other gas, which in the subsequent solution of the grain came 

 out in the form of one or more bubbles, and immediately dis- 

 appeared, by solution, in the surrounding reagent. 



One or two minutes after the application of Chlorzinc Iodine 

 to the grains (a little of the tannin solution remaining on the 

 slide, and therefore somewhat diluting the reagent) here and 

 there a grain can be seen to swell into an irregular mass, and 

 turn of a bluish colour ; most of the grains are however totally 

 unaffected, but in the course of a few minutes here and there 

 one shows, without swelling, a blue tint, varying in intensity 

 in the same grain from dark blue at one (the narrow) end, 

 gradually getting paler towards the other (and broader), while 

 this latter appears covered with irregular dark-blue spots, on a 

 pale reddish -blue ground. In the course of a few more minutes 

 some other grains have swollen and become blue ; but it is evident 



whole as much Iodine as it will take up. The solution will now have the consistence 

 of concentrated sulphuric acid, is perfectly clear, of a bright golden-brown colour, 

 slowly becoming somewhat darker on exposure to light. It can be brought to 

 various degrees of dilution, as its action varies according to its strength. It is best 

 kept in the dark. 



1 The tannin is of course non-essential. The results are the same with distilled 

 water. 



