294 EXPERIMENTS ON POTATOES WITH DIFFERENT MANURES. 



contain, according to the tables, 21-69 per cent, starch, and 28*9 

 dry matter, but in reality I found by analysis that the actual 

 amounts were 24-98 and 30-36 (Plot 18). 



Again, no definite relationship exists between the starch and 

 the amount of nitrogen (see Table V.), whether we consider the 

 nitrogen in the form of coagulable albuminoids, or the total 

 nitrogen present in the other compounds, as well as in the albu- 

 minoids ; but, on the whole, a reduction of starch is accom- 

 panied by an increase in nitrogen. 



Table VII. — Showing Average Percentage of Starch ohtcdned ivitli 

 'various Manures, and an Analysis of the Aggregate Averages. 



A cursory glance at the table of averages shows that bone 

 superphosphate, alone or mixed, produced tubers with a higher 

 percentage of starch, the mean results being for bone super- 

 phosphate 24-52 per cent, mineral superphosphate, 24*13 per- 

 cent., and " coprolites," 22-26 per cent., so that there was a gain 

 by employing the dissolved phosphate ; and it should also be 

 noticed that the maximum amount was produced when the 



