72 The Potatoe Plague. 



Water. Starch. Dry fibre. 



No. 1, Black Kidneys, Unripe, 68.7 17.7 13.5 



No. 2, do. do. ' Ripe, 72.0 17.9 10.0 



No. 3, Round Reds, Unripe, 69.8 15.1 15.0 

 No. 4, do. do. Ripe, 73.8 17.9 8.2 



The proportion of water in the unripe samples here seems 

 to be four per cent, less than in the ripe samples, having been 

 taken up some weeks earlier, and kept out of the ground 

 until the others were considered ripe enough. Neglecting 

 the water as unconnected with the present inquiry, we find that 

 the proportion of starch to the other solid matters is as 

 177 : 135 in the unripe kidneys, but as 179 : 100 in the ripe ; 

 or reducing both to a common measure, he have : 



Starch: other solid matters : : 131 : 100 in the unripe kid- 

 neys. : : 179 : 100 in the ripe do. 



In the round reds reducing as before to a common meas- 

 ure : 



Starch : other solid matters : : 100 - 100 in the unripe reds. 



216 - 100 in the ripe do. 



In each case it thus appears that the proportion of starch 

 to the other solid matters had increased considerably in the 

 interval which had elapsed between taking up the ripe and 

 unripe parcels. The remark will probably be made here, 

 that though an increase of starch has undoubtedly taken place, 

 yet the quantity present was considerable before, why then 

 should an addition to it injure the germinating power of the 

 set ? To answer this question it is necessary to state briefly 

 the doctrine propounded by the most eminent vegetable 

 physiologists of the present day, who affirm that during the 

 act of commencing germination a substance called " diastase," 

 is generated from the nitrogenous substances contained in 



