65 



FARMERS REGISTER, 



[No. 2 



The young stem, on the contrary, growing by the 

 increase of parts alreatly formed, has liom i(s first 

 dcvelopement, a tendency to grow in the direction 

 in wliich the bud points. If, in consequence ol the 

 buds pointing obli(|uely, the young stem slioois in 

 an oblique direction whilst yet beneath the surface 

 of tlie soil, the juices accumulate on the lower 

 side, and thus causing it to elongate more rapidly 

 than the upper side, the erect position of the stem 

 is restored. The bud (i'oni which the stem grows 

 contains every part of that stem, and all its ap- 

 pendages, in miniature. If the axis of this bud, 

 i. e. the stem in miniature, points perpendicularly 

 upwards, and its alier-growth is effected simply by 

 the enlargement ol these points, it is [)lain, that 

 the stem must have the same direction as the 

 axis of the bud ; or, in other words, must tjrovv in 

 the direction in which the bud points. The root 

 does not grow from a bud, but increases in size by 

 the addition of sepaiate portions of semi-fluid mat- 

 ter to its extremity; it will, therefore, increase 

 downwards, for just the same reason that an icicle 

 does. If this explanation be the correct one, it 

 will follow, that when, in a germinating seed, the 

 root happens to point directly upwards, and the 

 stem directly downwards, the two parts should 

 grow in these directions; yet^ being in a slate of 

 unstable equilibrium, the slightest variation li'om 

 a vertical line would cause them in time to resume 

 their proper directions. In confirmation of this 

 view, DeCandolIe placed a hyacinth in water, and 

 having fixed its bud so as to point directly down- 

 wards, caused its stem to develope in that direction. 

 Mr. Knight, to whom we are indebted for tliis 

 explanation of' the downward tendency of the 

 root, has tested its correctness by the following 

 very ingenious experiment, lie constructed a 

 wheel, and on its circumference fiastened a quanti- 

 ty of moss. In this moss he placed a number of 

 beans; and by means of a stream of water, which 

 served at the same time, to moisten the seed, 

 the wheel was made to revolve vertically, at the 

 rate of 150 times in a minute. In this rapid revo- 

 lution, the seeds were subjected to the action of a 

 centrifugal force, acting in tlie same manner as 

 gravity; but much more powerfully, and in a dif- 

 ferent direction. After some days, the wheel was 

 stopped, and on examining the growing seed, it 

 was found that each young plant, had taken the 

 direction of the radii of the wheel, the root being 

 turned directly from, and the stem directly tovvards 

 the centre of revuluiion. This experiment was 

 varied, by causing the wheel to revolve horizon- 

 tally; and the result was, that when the wheel 

 revolved with a moderate velocity, the roots were 

 directed obliquely downwards and outwards, and 

 the stems obliquely upwards and inwards ; in obe- 

 dience to the joint action of the centrifugal force 

 and the attraction of gravitation. Tiie more ra- 

 ])id the revolution of the wheel, the nearer did the 

 axis of the plant approach to a horizontal direc- 

 tion; but when the wheel revolved slowly, the at- 

 traction of gravitation preponderatinir, the young 

 plants frrew in a nearly vertical direction. The 

 only objection which I have ever heard urtfed to 

 this explanation, is this : if the root desL'cn(l>! l)y 

 the action ol" gravity, liow is it that the lateral di- 

 vis^ions of the root ulien grow in a direction nearly 

 horizontal ? In answer to this, I would say, that 

 the lateral divisions of the root grow horizontally, 

 bt'cauae they meet with some obstruction to their 



perpendicular growth. The longest horizontal 

 roots are generally to be found lying between the 

 loose porous soil and the harder and more com- 

 pact substratum of earth beneath that soil; and 

 they grow in that direction, for just the same rea- 

 son, that the water (which certainly descends un- 

 der the action of gravity) collects to a greater or 

 less extent, in a horizontal sheet, at the same 

 place. 



Some parasitic plants, such as the common mis- 

 letoe (iiincum veriicillalum) furnish the only real 

 exceptions to this rule. These direct their roots, 

 (if indeed they can be called roots) towards the 

 stem of the plant on which they grow ; and al- 

 ways grow nearly at right angles to the part of 

 the stem to which they are attached. The na- 

 ture of the body, does not affect the result. The 

 seeds of the misletoe, if made to germinate upon 

 the surlace of a common ball, will turn all their 

 roots tovvards (he centre of that ball. The at- 

 traction of the body to which the mistletoe fixes 

 itselfj cannot be admitted even in this case, as the 

 cause of the direction which the roots take, as 

 Duirochet has shown by the Ibllowing experi- 

 ment. " I glued" says that distinguished bota- 

 nist ''a germinating seed of the mistletoe to one 

 end of a delicate copper needle, mounted upon a 

 pivot, a little ball of wax being placed as a coun- 

 terpoise upon the other extremity. I then placed 

 by the side ut" the needle thus prepared, a small 

 block of wood, at the distance of about a mille- 

 metre (nearly one-twentieth of an inch) from the 

 radicle. The apparatus was next covered with a 

 glass shade, so that no external cause could dis- 

 Turb the needle. In five days, the young plant 

 began to direct its radicle towards the piece of 

 wood, the needle not changing its position, al- 

 though it was extremely moveable. In two days 

 more, the radicle was directed perpendicularly to 

 the block, the point being in contact with it, and 

 yet the needle had not moved in the slightest de- 

 gree." On this experiment it is sufficient to re- 

 mark, that had any attraction been exerted by the 

 block, upon the root, instead of causing the end of 

 that root to be turned up, and sustained in a hori- 

 zontal direction, it should have caused the needle 

 to move around, so as to touch the block. The 

 reason why the roots of a parasitic plant turn to- 

 vvards the stem of the plant on which it grows, 

 we must at present look upon as one of the secrets 

 of nature. Perhaps at some fliture day, when 

 vegetable physiology has been more studied, and 

 is better understood, we may be able to explain 

 the mystery. Except in the case of parasitic 

 plants, the root shows an invincible tendency, to 

 grow downwanls into the soil, whilst the stem, 

 shows an equally invincible tendency to grow up- 

 wards into the air. 



A second peculiarity of the root is, that it forms 

 no buds, whilst the stem always forms them. As 

 roots (brm no buds, and of course develope no 

 leaves, I hey present neither scales, which are the 

 rudiments of leaves, nor scars, which are the ves- 

 tiges of them. These remarks, however, are to 

 be understood as applying to roots and stems in or- 

 dinary circumstances onl}'. In extraordinary cir- 

 cumstances, the roots of some plants have the 

 power of forming buds, which are hence termed 

 adventitious buds. So also the stem, which, in 

 ordinary circumstances, has not the power of put- 

 tin" Ibrth roots, in extraordinary circumstances, 



