Busk on Starch- Granules. 
67 
thrown in the contracted state, and that this is the case seems 
to be shown by the immediate effects of re-agents. The first 
change, after a slight swelling of the starch-grain, consists in 
the appearance of minute transparent elevations around thq 
edge of the grain, as shown in fig. 6, each of which, I con- 
ceive, represents the edge of a fold or ruga ; a further stage of 
expansion is shown in fig. 7, and a still farther one in fig. 
8 ; whilst the full expansion of the vesicle in Tous les mois 
is shown in fig. 9. I believe, also — but of this I would speak 
very doubtfully — that each starch-vesicle has an opening 
which corresponds with the central spot or hilum. With 
respect to the contents of the vesicle, some appearances lead 
me to suppose that, occasionally at all events, it contains a 
flocculent or grumous material — amorphous starch, which is 
equally coloured by iodine, as is the wall itself of the vesicle. 
There is sometimes also an appearance of a transparent 
colourless wall around these grumous contents, in a form of 
arrow- root I have examined ; but an outline of this kind is 
often a very deceptive phenomenon, and I do not wish to be 
understood positively to assert its existence even in the case 
alluded to. 
Two additional modes, which I have found convenient in 
the examination of starch, consist: — 1st. In the previous 
roasting of the grain till it acquires a light-brown colour, and 
is, in fact, converted into British gum ; while in this state, 
if it be moistened with a very weak solution of iodine, the 
grain gradually unfolds itself in the most beautiful manner. 
2. The iodized solution of chloride of zinc, proposed by Pro- 
fessor Schultz, may also be very advantageously employed. 
This solution, if quite concentrated, does not at first colour 
the starch at all, but, on the addition of a little water, the 
blue colour is elicited, and the starch-grains gradually swell 
out and evolve themselves in the same way as they do under 
the previously described treatment. I make the iodized so- 
lution of chloride of zinc by dissolving 1 ounce of fused 
chloride of zinc in about half an ounce of water, and adding 
to the solution (which amounts to about an ounce fluid mea- 
sure) 3 grains of iodine dissolved, with the aid of 6 grains 
of iodide of potassium, in the smallest possible quantity of 
water. 
Since the above paper was read, I have noticed appear- 
ances in the amylaceous corpuscles which occur in the wall 
of the primordial utricle of Hydrodictyon utriculatum, which 
lead to the opinion that the starch — in this case at least, 
