THE FA 



ERS' REGISTER 



Vol. VII. 



FEBRUARY 28, 1839. 



No. 2. 



EDMUND RUPFIN, EDITOR AND PROPRIETOR. 



For the Fanners' Register. 

 ESSAY ON VEGETABLE PHYSIOLOGY. 



(Continued from page 17, last No.) 

 Chap. III. 



DIFFERENCE BETWEEN THE ROOT AND STEM; 

 1st. IN THE DIRECTION OF THEIR GROWTH ; 

 2d. IN THE ABSENCE OR PRESKNCE OF BUDSJ 

 3d. IN THE MANNER OF THEIR GROWTH. 



Having completed our examination of the ele- 

 mentary vegetable structures, and of' the organs 

 formed immediately from them, viz : the cellular, 

 woody, and vascular tissues ; we will now com- 

 mence our investigation into the structure, and 

 vital action, of the compound organs of plants. 

 These, as has been already mentioned, are divi- 

 ded into two classes; according as they are in- 

 tended to minister to the growth of the plant, or 

 to the production and perfection of the Iruit. The 

 lirst class, including the root, stem and leaves, 

 being termed organs of vegetation ; and the se- 

 cond, including the calyx, corolla, stamens, and 

 pistils, being termed organs of fructification. 



The root and stem, we will examine in connex- 

 ion. The central part, or axis of a plant, that part 

 to which all the other parts are attached, consists oi' 

 two distinct poriioiis; the ascending portion, or 

 stem, and the ilescending portion, or root. The 

 common deliuiiion of the term root, is "that part of 

 the trunk which fixes the plant to the soil, and bur- 

 rows beneath its surface." This definition will 

 answer as a popular one ; but if we wish to get a 

 more correct idea of the nature of the root, it will 

 be necessary to attend to the difierences whu-h 

 exist between it and the stem a little more in 

 detail. 



One of the most striking peculiarities of the root 

 is in the direction of its growth. If a seed be 

 placed in the ground, in favorable circumstances, 

 the embryo plant within it soon l)egins to grow in 

 two opposite directions; one of its extremities 

 manilesiing an invincible tendency to grow up- 

 wards into the air and light, and the other an 

 equally invincible determination to the earth, away 

 from ihe light. If after a seed has sprouted its 

 position in the ground be reversed, so that the stem 

 shall point downwards and the root upwards, they 

 will both twist entirely around, in order to develope 

 themselves in their proper media. This fact is com- 

 monly explained by saying, that the root is attract- 

 ed by the moisture' of the earth, whilst the stem is 

 attracted by the air and light. It is, to say the least, 

 a very loose use oflani^uage, to talk about the at- 

 traction of the root, ibr moisture, or of the stem, 

 for air and light. Attractions are those forces 

 which different portions of matter exert on eacli 

 other, tending to bring those portions together. If 

 a particle A, be attracted by another particle B, of 

 equal size, the force exerted is as much exerted by 

 A as it is by B ; and the tendency of A to move 

 is no greater than that of B. If one of these bo- 

 dies be in any way fixed, it is plain, that all the 

 movement must be made by the other. Such are, 

 in fiicl, the circumstances in which the yount^ root 

 Vol. VII-9 



of a plant and the moisture of the earth are placed. 

 The young root is fixed, whilst the moisture is 

 moveable. If then there is an attraction between 

 the two, the moisture should move up towards the 

 root, and not the root down towards the moisture. 

 The same remark will apply with even greater 

 force to the supposed attraction between the stem, 

 and the air and light. One of the facts which 

 is most frequently lirought forward in support of 

 thi3 notion of attraction is, that when a plant is 

 placed in a dry and barren spot, in the immediate 

 neighborhood of a more moist and fertile one, iie 

 rooTs are always found to increase more rapidly in 

 the direction of that moist and fertile portion than 

 in any other. This, as we shall hereafter see, is 

 not owing to any attraction exerted by the mois- 

 ture ujion the roots, but to an cntirel}' dillereut 

 cause. 



This matter has been put to the test of direct 

 experiment. Dutrochet filled a box wiih moist 

 earth, and having jiierced the bottom with many 

 holes, he placed within the box, and near to its 

 lower surface, a number of beans, and then sus- 

 pended it in the air about eighteen feet from the 

 ground. The seed being thus situated, it should 

 Ibllow, that i!" the young stem is attracted by the 

 light, and the root by moisture, the Jbrmer should 

 shoot downwards into the air, and the latter up- 

 wards into the mois! earth. This, iiowever, did not 

 take place; l)Ui, on the contiaiy, the nidicles de- 

 scended into the amiospliere, where they soon 

 dried up and pcrisiii'd; whilst ihe stems ascended 

 vertically, lorciiig their way into the earth. He 

 then placed some of the saiall plants so that their 

 roots poinied directly up into the soil; but instead 

 of fixiiiir ihemselvoa therein, their |!oin(s soon 

 turned aiouiul, and grew in an opposiie direction. 

 Supposing that possibly the quan'ity of earth might 

 affect the direction of their growth, he afterwards 

 made use of a much larger box, and accumulated 

 a very considerable mass of earth above the seed, 

 but the result was the same as before; thus prov- 

 ing that the stem is not aitracted by air oriitjlit, 

 neither is the root repelled by light or attracted by 

 moisture. 



That the radicle is not attracted by moisture, the 

 same naturalist afterwards proved more directly by 

 another experiment. He susj)ended in a glass jar a 

 piece of sponge, so placed as to present a flat verti- 

 cle surface in one direction. One end of this piece 

 of sponge was made to di[) into a cup of water, so 

 that it might always be kept filled with water. He 

 then suspended within the same jar, a germinating 

 bean ; bringing its radicle as near to the vcrticle 

 face of the sponge as was possible, without touch- 

 ing it. In this case, if any attraction had been ex- 

 erted upon the root, by the moisture of the sponge, 

 a slight turn of the former would have brought 

 them in contact. The radicle, however, grew 

 perpendicularly, manifesting no tendency to turn 

 towards the sponye. The true explanation of this 

 matter appears to be this: that as roots lengthen, 

 by the addition of new matter to their extremities, 

 in a soft or semi-fluid state, liieygrow downwards, 

 under the action oi' the attraction of gravitation. 



