GROWTH OF TUKNIPS AND OATS COMPARED. 53 



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 turnip, the former must have ac- 

 cumulated 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 

 vegetation. The mass of organic substances accumu- 

 lating 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 shooting for extracting these nutritive 

 substances from the ground. Now if the turnips and 

 oats growing on a hectare (2-J- acres) of land had daily 

 received an equal amount of them, then, all other cir- 

 cumstances 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 ab- 

 sorbent root-surface. The larger root-surface is in con- 

 tact with more earthy particles, 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 azo- 

 tised materials, depend upon the nature of the plants. 

 If the absorbent root-surface of the oat-plant were 2*45 

 times greater than that of the turnip, the former would, 

 under like circumstances, take up daily 2*45 times as 

 much food as the latter, i. e. the oat-plant would absorb 

 in 50 days as much as the turnip in 122 days. Thus 

 in equal times the power of two plants to absorb food is 

 in proportion to their absorbent root-surface. 



The time of vegetation occupied by the turnip-plant 

 comprises, in the first year, 120 to 122 days, and termi- 

 nates at the end of July in the next year with the pro- 

 duction of seed. If we take the whole time of vegeta- 

 tion of the turnip-plant at 244 days, and suppose the 

 time of vegetation of the oat-plant extended from 93 or 



