1839] 



FARMERS' REGISTER. 



425 



was merely in a state of separation from the at- 

 mospheric air which had been inhaled and de- 

 prived of its oxygen and carlioiiic acid. But its 

 constant occurrence in comhiuation with the tissue 

 of mushrooms, and crucilorm planis, in gluten, 

 and in what chemists call vegetable albumen, and 

 also in the vegetable alkalies, seeins a sufHciently 

 strong proof of its contributing in some way or 

 other, to the nutrition of the vegetable system." 

 In what condition the nitrogen enters the system 

 of a plant, is a question which has never as yet 

 been satisfactorily settled. The most probable 

 answer is, that it is absorbed by the leaves, from 

 the atmosphere. At any rate, this much is cer- 

 tain, that leaves do absorb much gaseous maiter 

 irom the atmosphere, and that nitrogen e.xists in 

 very large quantities in the atmosphere; accord- 

 ing the best analyses y",f,y of our atmosphere are 

 nitrogen. It is probable that a portion also enters 

 in solution in water, like carbonic acid. It is true, 

 that nitrogen is by no means as soluble in water 

 as carbonic acid, water dissolving only about ^fn 

 of its bulk of niirogen; but yet when we call to 

 nund tlie vast quantity of water which passes 

 through the system of a plant during its growth, 

 and remember at the same tiirie the small extent 

 to which niirogen enters into the cimiposilion 

 of vegetables, we will see that no inconsidera- 

 ble portion of it may have entered in this way. It 

 is possible also, that a port ion of nitrogen may en- 

 ter, in combination with other substances, and be 

 afterwards separated from its combinations, and 

 fixed by the vital action of the tissues of the plant; 

 in just the same way in which carbon is separated 

 from its combination with oxygen in carbonic 

 acid. There are several compounds which expe- 

 rience has proven to be very valuable as manures, 

 which contain nitrogen. Ammonia is one of these; 

 its composition is, by weight, 3 parts of hydrogen 

 to 14.15 of nitrogen. The salts of ammonia exist 

 in large quantities in common soot, and tliis is 

 known to be a very active manure. It is true that 

 soot is generall}' classed among stimulating ma- 

 nures, but may it not he that it stimulates the 

 growth of a plant, simply by furnishing one of its 

 necessary articles of Ibod 7 What renders this opi- 

 nion the more probable is, that soot is found to be 

 a manure particularly efficacious in the case of 

 crucilorm plants, (('. e. plants whose flowers con- 

 sist of ibur petals arranged in the Ibrm of a cross, 

 such as the cabbage, turnip, &c.,) and these are 

 the plants which contain the greatest quantity of 

 nitrogen. 



Besides carbonic acidjwater, and niirogen, which 

 form what may with propriety be called the food of 

 plants, there are several earthy and metallic sub- 

 stances, which are taken up from the soil in con- 

 siderable quantities, by certain plants, and al'ier- 

 wards deposited in their tissues. About the part 

 which these substances act in the economy of ve- 

 getable life, we know but little. ''One of the most 

 remarkable of these is silex, which is secreted by 

 certain plants in very great quantities. All grasses 

 abound in it ; usually it fixes itself in the cuticle ; 

 but in the bamboo it is also deposited in considera- 

 ble quantities in the hollow joints, under the form 

 of the substance called tabaslieer. The skin of 

 the rattan palm, abounds so much in silexthat it 

 will strike tire with steel ; the same substance ex- 

 ists in teak and other kinds of wood, to which it 

 gives a peculiarly gritty texture: and in the scour- 

 VoL. VlI-54 



ing rush, {equisetum,) one species of which is 

 used for polishing wood, in consequence of its 

 whole surface being composed of compact sili- 

 cious particles. It was once thought that silex 

 must be actually formed by the action of the vital 

 principle of vegetation ; but further investigations 

 into the nature of silex, have shovv^n that in cer- 

 tain circumstances, silex is soluble in water, and it 

 is more probable that it is in this way that it en- 

 ters plants. Considering the immense quantity of 

 water that passes through a plant in the course of 

 its growth, there is no difficulty in conceiving the 

 possibility of the largest quantity of silex, wiiich 

 is ever met with in plants, being introduced in tiiis 

 way.'' But even if we could not account lor the 

 introduction of silex into plants, we could by no 

 means admit that it was formed by the vital action 

 of plants themselves ; inasmuch as with such an 

 admission, we must also admit that plants pos- 

 sessed, either a creative power, or else a power of 

 transmuting one of the simple elements into an- 

 other ; an admission which contradicts the best 

 established laws of chemistry. 



Lime, magnesia, polassa, soda, sulphur, phos- 

 phorus, and several of the metals, occur in many 

 plants in greater or less abundance ; all evidently 

 taken up from the soil. "Of these soda is the 

 best known and most abundant, existing to tiie 

 amount of as much as 55 per cent-, in the form of 

 a carbonate in the ashes of' a species of sea-v.'eed 

 (salsola saliva;) and copper, the least suspected 

 and most curious. This metal is stated by De 

 Candolle to form eight parts in a miilion in cotlee, 

 and about four and a half parfs in a million in 

 wheal ; whence he has calculated that there is 

 annuall}' imported into Kurope more than 1200 lbs. 

 weight of copper in collide, and that the French 

 annually consume nearly 8000 lbs. in their bread. 



Our knowledge ol'the nature ofthe food ofplants, 

 will enable us to explain some facts which have 

 been established by experiment, lor instance, the 

 manner in which clover improves land, and may 

 perhaps suggest other rules to the practical agri- 

 culturist. Had we no experience on the subject, 

 it would seeiTi, to say the least, improbable that 

 any crop coidd improve land. We would naturally 

 suppose that plants were nourished by the ground 

 itself,— that they fed upon the .soil. If such he 

 the case, when a crop is ploughed under and de- 

 decays, it can give nothing but what it has first 

 taken; and hov/ then can it improve land ? Yet 

 we find that growing clover upon land, and then 

 ploughing it under and suflerinir it to decaj', is one 

 of the very best methods of improving land. 

 Bearing in mind the nature of the Ibod of plants, 

 this admits of a verj^ simple explanation. We 

 will suppose that clover is sown upon a perfectly 

 l)arren spot. The atmosphere which is above this 

 spot contains a portion of carbonic acid gas, for 

 all atmosph&ric air contains a greater or less por- 

 tion of it. A rain comes ; as it fall^, it absorbs a 

 portion of this gas, and in this condition enters the 

 ground. No sooner does it come in contact with 

 the seed in the first instance, and with the root 

 afterwards, then it is absorbed and its maferialg 

 used Ibr increasing the size ofthe vegetable struc- 

 ture. When the portion of air above the spot, 

 has in this way been exhausted of carbonic acid, a 

 supply is obtained fi-oin the neighbouring portions 

 in consequence of that strong tendency which 

 gasses possess, to intermix and diffuse themselves 



