88 M. Miiller on the Germination o/Isoetes lacustris. 



fact, when it is acted on by iodine it also becomes coloured blue, 

 and the result is that the said compact granule is transformed 

 into an amylum-cell. This transition of the granule is actually 

 very easy to trace when once we are aware of the connexion of 

 the facts. All the intermediate stages between the original com- 

 pact granule and the amylum-cell may readily be discriminated 

 by the application of iodine. Moreover the granules become 

 converted into starch at an extremely early epoch, before we can 

 yet regard them as amylum-cells. 



In my ' History of the Development of the Lycopodiacese ' I 

 mentioned a remarkable peculiarity of these amylum-cells, viz. 

 that the blue colour produced by iodine very readily disappears 

 again in certain amylum-cells, and that it may be restored just 

 as readily by touching the cells, or often merely by rolling them 

 backwards and forwards in the water ; indeed, that one may often 

 continue this alternation at one's pleasure for a long time. This 

 peculiarity is equally characteristic of the amylum-cells of the 

 ovule of Isoetes. The phenomenon appears however only in the 

 larger cells, such as may be recognised as amylum-cells even 

 without the use of iodine. But neither here any more than in 

 Selaginella have I succeeded in discovering the reason of this 

 strange property. 



With regard to the structure of the amylum-cell itself — this 

 consists of more or less distinctly concentric layers deposited 

 round a central nucleus which becomes coloured intensely blue 

 by iodine (fig. 5). Several such dark groups often occur in one 

 cell, the central nucleus being constantly present. In larger cells 

 we may distinctly make out that these larger amylum-cells are 

 distinct discoid bodies, convex on both faces (fig. 5 a). They 

 frequently exhibit minute furrows, as is so often the case with 

 starch-granules. 



As soon as the granules are transformed into amylum they are 

 in a condition to enter into new combinations with the elements 

 of water. They swell up by the absorption of water, and then 

 become decomposed into that fluid matter so often mentioned, 

 which presents itself to the investigator in drops like oil. I have 

 already stated in my l History of the Development of Chara*,' that 

 I have directly observed this change, and I have there reported on 

 it at length. As in that case, where the process may be traced 

 more readily from the mere fact that the starch-cells are larger, 

 they become softened in water, retaining their shape, until the 

 whole of the contents comes into a fluid condition. Then they 

 burst and the contents are scattered, always in the form of drops. 

 I must therefore repeat here that the outermost layer of the 



* Ann. of Nat. Hist. Ser. 1. vol. xvii. p. 258. 



