no 



THE SOIL. 



What strikes us here at once is the great difference in 

 the number and weight of the seeds respectively gathered 

 from the several pots. The soil richer in nutritive sub- 

 stances yielded not only more, but larger and heavier 

 seeds, the average weight in miUigrammes being respect- 

 ively : — 



Of the seeds of the plants grown in the first pot (pure 

 turf), seven weighed no more than five of the beans 

 origmally sown ; whereas those of the plants grown in 

 the saturated turf weighed each l-5th more than one of 

 the seed-beans. 



If we compare the crop of seeds with the quantity of 

 nutritive substances contained in the turf of the four pots, 

 we see at once what influence the form and distribution 

 of the nutritive substances have exercised upon their 

 nutritive power. 



The l-4th saturated turf contained a Httle above one- 

 half (0-83 gramme) more phosphoric acid than that in 

 the pure turf (1-586 grammes) ; the potash was doubled ; 

 and the amount of nitrogen was increased only by -^^yth. 

 The crop, however, exceeded that obtained from the 

 plants grown in pure turf, not by Jrd (corresponding to 

 the quantity of phosphoric acid added), but it was thirteen 

 times as large. The feeble manuring had caused the turf 

 in the second pot to render thirteen times more nutritive 

 matter for the formation of seed alone, and for the entire 

 plants about thirty times more than the pure turf. 



It is evident that only a smaU proportion of the ash- 

 constituents in the pure turf were present in a form suit- 



