208 NUTRIMENT OF ORGANIZED BODIES. 



then the farmer may aid the plant in its growth by giving it organic matter as a fertilizer. 

 Carbon is, as it would seem, the only substance which is claimed to be furnished vegetables 

 from the atmosphere. Of gaseous matter, nitrogen and ammonia it is acknowledged must be 

 diffused through the soil, and taken up by the roots in solution and combination. The disap- 

 pearance of carbonic acid from a given volume of air, when it is made to pass over the leaves 

 of plants, may be due to a simple condensation upon surfaces. This condensation, of course, 

 must first take place ; but it does not necesarily follow that it is absorbed : other experiments 

 are required to put the question at rest. 



The nutriment of plants is of two kinds, one which conasts mainly of carbonaceous matter, 

 (organic ) and another in which mineral matter is the princpal ingredient. Both are important j 

 both must be added to the soil ; both are usually combined together, though the mineral matter 

 may and often is, added by itself, as when plaster and burnt bones are employed. Decayed 

 vegetables, barnyard manures, etc. consist of organic and inorganic matters, and there is little 

 doubt but that crenic and apo-crenic acids, in combination with mineral matters, form one of 

 the most important nutriments for plants. The office which mineral matter performs, in part, 

 in the vegetable tissues is to strengthen the texture ; it forms a skeleton, or frame w'ork. This 

 skeleton, as I have elsewhere observed, may be seen when all the organic matter is burned ; 

 and in all plants this f-keleton represents the arrangement of the mineral matter in the plant. 

 In some it is strong, in others it is weak ; the bark always furnishes a heavier skeleton than 

 the wood. Tliis skeleton is the ash. Grasses and culminiferous plants have a skeleton made 

 up mostly of silica, while in most plants it is a carbonate of lime and phosphate of lime, as ob- 

 tained by combustion. The bark of trees, as may be seen by analysis, consists of carbonate of 

 lime mostly, or a basis of lime in combination with an organic acid, when in its original condition. 



Aliment, before it can pass into the tissues of the plant, must be in the condition of inorganic 

 matter. Muscle or cartillage can not nourish an animal, until it has undergone a dissolution ; 

 it must be resolved into its elements, and the same fact exists in the vegetable kingdom ; none 

 of the or<Tanized products are in a condition to sustain life, until they have passed into an inor- 

 ganic state. 



There is no doubt now in regard to the importance of organic matter in the soil. The view 

 which has been maintained by physiologists of high standing, that the products of decomposing 

 vegetables were of little or no value, has been discarded. The view too that carbon may be 

 derived from the atmosphere in sufficient quantities to meet the demands of highly cultivated 

 crops is seen to be fallacious. It is now well known that a proper mixture of mineral and 

 organic or vegetable matter is essential to constitute a fertilizer. Plants differ, however, as to 

 their wants ; some require more mineral matter than others. It is with them as it is with many 

 plants in other respects ; some have a large root, and some have no root at all, or an exceeding 

 small root ; and some, too, are very leafy, others without leaves : hence a theory of nutrition 

 which is designed to comprehend all the facts and phenomena of the subject, must have regard 

 to many anomalous cases of vegetation and growth, as the leafless plant, the plant with heavy 

 succulent leaves, the air plants, mushrooms, lichens, etc. 



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