caiOWTIl OF TUllNIi'S AND OATS CO.Ml'AKliU. o[) 



any positive law of growth for those two plants : still a 

 few inferences may easily be drawn from them. The 

 quantities of phosphoric acid and nitrogen in the turnip 

 are, at the end of the first year of vegetation, nearly in 

 the proportion of 1 : 1 ; m oats, on the contrary, of 1 : 4. 

 The oat-plant requii'es to the same quantity of phosphoric 

 acid four times as much nitrogen as the turnip ; and the 

 latter to the same quantity of nitrogen four times as much 

 phosphoric acid. 



If the developement of the oat-plant takes a similar 

 course to that of the tm'iiip, the former must have accu- 

 midated in its underground organs before the time of 

 shooting a store of organisable matter, similar to that laid 

 up by the turnip at the close of the first year of vege- 

 tation. The mass of organic substances accumulating in 

 these plants before the developement of the flower-stalk is 

 manifestly much larger in the turnip than in the oat- 

 plant. The former receives from the soil much more 

 phosphoric acid and nitrogen ; but the turnip had 122 

 days, the oat-plant only 50 days, up to the period of 

 shootmg for extracting these nutritive substances from 

 the ground. Now if the turnips and oats growing on a 

 hectai'e (2^ acres) of land had daily received an equal 

 amount of them, then, all other circumstances being the 

 same, the quantity of nutritive substances absorbed would 

 be proportionate to the time of absorption. In this 

 respect the nature of the root makes a great difference, 

 according to the extent of absorbent root-surftice. Tlie 

 larger root-surface is in contact with more earthy par- 

 ticles, and can during the same time extract more nutritive 

 substances than the smaller. The mass of vegetable 

 substance produced, and especially the quantity of non- 

 nitrogenous and azotised materials, depend upon the 

 nature of the plants. K the absorbent root-surface of the 



