Agiicultuml CJiemistry — Turnips. 



533 



required in such a mechanical condition as shall render it easily 

 permeable to the atmosphere and to the fibrous roots of the 

 plants, — that healthy action and a tendency to development of 

 very extended underground collective apparatus should be induced 

 by the use of the so-called ''mineral manures," these never being- 

 in an alkaline state, and always containing a considerable quantity 

 of phosphoric acid easily available to the plant, — that after the 

 early stages of the plant are passed, its rapidity of growth de- 

 pends upon an abundant provision in the soil of constituents for 

 organic formations, especially of carhon, — that nitrogen must be 

 provided by cultivation, though seldom by special manures, — 

 and lastly, that all these requisites being provided by the farmer, 

 the degree in which his efforts will be availing depends essentially 

 upon certain climatic conditions, comprising a considerable con- 

 iinuity and amount of rain as a means of taking up the stores 

 of the soil, keeping up a vigorous circulation in the plant, and 

 supplying the dissolved gases of the atmosphere. 



These conditions compared with those which are required in 

 the culture of wheat are opposed to one another in almost every 

 particular, but as we proceed we shall see, that of the observed 

 differences much is doubtless due to the essential distinctions 

 between the tendencies of the natural families to which the plants 

 belong; yet much of it is also attributable to the fact, that in the 

 case of the turnip it is not the seed that is the object of our 

 culture, but a monstrous accumulation which could only take 

 place under a somewhat unnatural or artificial balance of the 

 constituents of supplied food, and under such a condition of 

 climate as should be adverse to seed-forming. 



It is known that where the turnip is grown for its natural seed- 

 product, oil, a heavier soil, richer manuring, and, during a con- 

 siderable period of the growth of the plant, a much higher tem- 

 perature, are required than when the bulb is to be produced. 

 Under these circumstances there will be much less fibrous root 

 thrown up to the surface, — the root is scarcely bulbous, but fusi- 

 form, tapping rather than spreading laterally; the leaves and 

 stem are much larger, both actually and proportionally to the 

 root, and the organic manures should contain more nitrogen and 

 less carbon. Were we then to cultivate the turnip for its most 

 natural products, the treatment it would require would much 

 more nearly approach that adapted for wheat than at present ; 

 the deviations from it now observed, and which have been referred 

 too exclusively to the natural specialities of the plants, w^ould be 

 greatly lessened, and the character of the plant as a ''fallow crop''' 

 would be lost. It is no objection to this assumption that in 

 selecting plants to transplant for seed from lohicli to grow bulb 

 those having the inost symmetrical bulb are chosen rather than 



VOL. VIII. 2 N 



