STARCHES. 143 



indeed, in conjunction with the chemical tests above referred to, is 

 all in all in the determination of the kind of starch, or source from 

 which any variety of starch may have been obtained. Looking at 

 any sample of starch, we perceive it under the microscope to 

 consist of more or less rounded particles, which, if moist, will be 

 seen to be marked with certain concentric rings surrounding a spot 

 called the hilum. Old observers considered these granules in the 

 light of cells, the rings being markings on the cell wall, whilst the 

 hilum represented the point of attachment to the wall of the 

 primary cell wherein they were enclosed. 



A section of any tuber or starch-containing seed before ger- 

 mination — such as the pea — will show the fallacy of this ; the 

 granules, though certainly contained in cells the same as any other 

 cell contents, are not attached either to the cell-wall or to each 

 other, but appear to be merely deposited therein, and to act as a 

 reserve store for the future formation of cells. Thus, although the 

 cells in a pea are full of starch before germination, yet let germi- 

 nation once ensue, after some two or three days iodine no longer 

 produces the magnificent blue colour indicative of starch, but the 

 browner tint showing the transformation into dextrine, and after 

 from ten days to a fortnight no trace of starch granules are visible, 

 all having been dissolved by the diastaste, and left the cells 

 wherein they were deposited to produce cells in the young shoots, 

 before the formation of roots enables nourishment to be extracted 

 from the soil. This may be beautifully illustrated by observing 

 two sections of pea under the microscope, one being cut before 

 germination ; the other ten days after. 



How, then, are starch-grains produced ? From what are they 

 formed ? Do they grow in layers, as would seem to be indicated 

 by the markings ? and if so, are these layers deposited from within 

 outwards, as would be the more natural supposition, or in the 

 opposite direction ? Many observers have worked on this subject, 

 amongst whom I may mention Raspail, Fritzsche, Buck, AUman, 

 Criiger, Schlieden, Virchow, Raine, Nagelli, and Sachs. These 

 are only a few of the names of workers in this subject who have 

 attempted to elucidate the growth of the starch granule, nearly 

 every observer coming to a slightly different conclusion to others. 



The observers on the subject may, however, be divided into 



