Vol. 6. 



GENESEl! FARMER. 



35 



of the sun. This is called the plume, or plumula, 

 from which leaves are developed, and the trunk; or 

 stem, is formed. 



The roots of plants are only the prolongation of 

 the woody fibres and bark of the stem into the earth. 

 The inner bark is called the coriich; and the outer 

 the epidermis. Both of these membranous cover- 

 ings of plants extend over all their roots, and are 

 perforated by innumerable pores, called spongioles, 

 or little sponges. The woody portion of roots is 

 also very porous and spongy, so as to permit the 

 easy ingress and egress of water, or sap. 



All new roots put forth have their origin in the 

 alburnum, or white sap-wood, that surrounds the 

 hca rl-icood, as it is called in forest trees. It is 

 through the numerous tubes or vessels in the sap- 

 wood, which extend from the roots to the leaves of 

 plants, that all liquids pass up to the latter organs. 

 These liquids descend in vessels that lie in the cor- 

 ticle, or inner bark. 



The obvious function of roots is to imbibe liquid 

 nourishment from the soil, that it may pass up and 

 supply, in part at least, the wants of the living be- 

 ing. It is a question of considerable importance, 

 whether roots have the power to discriminate as to 

 what substances they will admit as suitable food, 

 i;nd what reject as improper or poisonous. This 

 is still an open question. Liebig, Dumas, and Bous- 

 singault, find reason to believe that roots act mecha- 

 nically, like a sponge, and take in whatever sub- 

 stances may be held in solution in the water that 

 enters their pores. Other physiologists, of equal 

 distinction, believe that roots are endowed with a 

 kind of elective alfinity under ordinary circumstances, 

 which selects what is needed to accomplish the pur- 

 pose of nature, and cxchides matter which would 

 t'ounteract that purpose. 



If the stem or root of a vegetable be placed in a 

 vessel of water, and the quantity not large, it will 

 all be taken up, and either decomposed to furnish al- 

 iment to the plant, or it will be dissipated into the 

 air from its leaves. When the supply is exhausted, 

 the leaves and flowers wither, or dry like herbs and 

 hay. In the summer season, and under the influ- 

 ence of a hot sun, the leaves of corn and clover curl 

 up, because the evaporation from their surface ex- 

 ceeds the supply of moisture from their roots. 



It is probable that the circulation of a plant is 

 most active v^hen the temperature of the atmosphere 

 is such as to cause a free evaporation from its leaves, 

 Vv'ithout drying them. The chill of evening, and 

 even clouds, by checking evaporation, will enable the 

 ascending sap to restore freshness to drooping 

 plants without the aid of any moisture from the air. 

 But to render their resuscitation doubly sure, nature 

 usually condenses vapor in the form of dew, which 

 supplies these organs, not only with water, but with 

 carbonic acid, and otlier gases imbibed by the leaves, 

 and used as food to nourish plants. 



If a few leaves on a growing plant be bent over, 

 EO that they may be placed under a tumbler inverted, 

 and full of w'ater, and the leaves thus fixed, be expo- 

 sed to the direct rays of the sun, bubbles of gas will 

 be seen to form on the leaves, and gradually rise and 

 collect in the bottom of the tumbler. If this gas be 

 examined, it will be found to be pure oxygen. 



If the water contain carbonic acid, it will gradu- 

 ally disapijear, and an equal bulk of pure oxygen will 

 be left in its place. 



This demonstrates the important fact, that leaves, 

 when subjected to the direct rays of the sun, have 



the power to decompose a compound of carbon and 

 oxygen, which is always formed hy the bur ning, fer-- 

 menting, and rotting of vegetables, and by the /-ce- 

 piration of all animals. 



As carbonic acid exists in immense quantities in 

 stratified rocks, particularly limestone and magnesia, 

 it may be regarded as a mineral substance. Its im- 

 portant constituent — carbon— forms about 60 per 

 cent., and sometimes 90, of mineral coal. While 

 there are many situations, or operations in nature, in 

 which carbon and oxygen unite to form carbonic 

 acid, it is worthy of note that this compound is no 

 where decomposed except in the organic laboratory 

 of plants, and that by the action of the light of tho 

 sun. Both its carbon and oxygen are indispensable 

 ingredients in building up the bodies of all animals ; 

 but not one of them can decompose either carbonic 

 acid or water, and thus obtain the carbon, oxygen, 

 and hydrogen necessary to form animal fat and mus- 

 cle. Plants alone have this power. 



It sometimes happens that the quantity of oxygen 

 given oflT from leaves is less than the quantity im- 

 bibed in the carbonic acid. This fact is accounted 

 for by the analysis of the plant, which shows that a 

 portion of the oxygen has entered into the compo- 

 sition of the organic substances of the vegetable. 

 On the other hand, Sprengel has demonstrated, that 

 when plants arc watered with liquids containing car- 

 bonic, sulphuric, or nitric acid, the quantity of oxy- 

 gen given off" by the leaves is greater than that im- 

 bibed from the air. Thus demonstrating, that those 

 acids, when taken in by the roots, are decomposed ; 

 and as the excess of sulphur does not escape by the 

 leaves, nor remain in the plant, it is inferred that it 

 must make its exit from the plant by its roots. 



" AMERICAN QUARTERLY JOURNAL OF 

 AGRICULTURE AND SCIENCE." 



Under the above name Prof. Emmons, of Albany, 

 and Dr. Prime, of Newburgh, have commenced the 

 publication of a handsome Quarterly of 200 pages, 

 for the purpose of bringing to the aid of practical 

 agriculture more science than has hitherto been done 

 in this country. We hope that their eftbrts in this 

 laudable enterprise will be crowned with success. 

 There is enough of scientific attainment already de- 

 voted to the profession of agriculture to sustain a 

 work of this character, if it can be placed under the 

 inspection of all who will feel an interest in reading 

 its pages. To medical gentlemen, who are more or 

 less engaged in rural pursuits, and to all that have 

 studied the sciences of geology, chemistry, vegetable 

 and animal physiology, this Quarterly will be of 

 great value, while common, plain farmers will also 

 find in it much to interest and instruct them. 



Its leading article, " On the Food of Plants," is a 

 well-written essay from the pen of Dr. ITun. He 

 follows the theory of Liebig, Dumas, and Boussain- 

 ganlt. Dr. H. has somehow fallen into the common 

 error of regarding the "salts of soda, potash, ah':- 

 mina, silex, and other earthy and saline matters," as 

 " not forming any part of the organized tissues of 

 plants." He says, " they are simply deposited in 

 these tissues, and are called the inorganic constitu- 

 ents of plants." On the contrary, carbon, oxygen, 

 hydrogen, and nitrogen are regarded as organic ele- 

 ments", whether organized in plants and aniniah, or 

 in the form of carbonic acid, vapor, and ammonia, in 

 the air. This arrangement is not only not true to 

 nature, but it dcfctroys all distinction between unor- 

 ganized carbon, oxygen, hydrogen, and nitrogen, 



