100 THE ROOT. 



has its situation naturally in the earth, it descends perpendicu- 

 larly to its surface. Previous to his investigations, various 

 hypotheses were abroad to account for the uniform direction of 

 the root and stem ; but all were unsatisfactory. If seeds are 

 permitted to sprout in a box, and after the plumula and radicle 

 are developed in their common directions, the box be inverted, 

 the root will change its direction downward, and the plumula 

 upward ; and if they are permitted to sprout in a tube in 

 which they cannot turn after inversion, they will assume a 

 spiral form. The cause in these cases is made plain by a curi- 

 ous experiment contrived by Dutrochet. It was found that the 

 Mistletoe had the same impulse toward the center of the 

 branch of a tree on which it grows that most other plants have 

 to the center of the earth ; and it was also found that the Mis- 

 tletoe might be made to germinate on a thread so small that it 

 would exercise no influence over the direction of the root. This 

 he did, and then fixed it to a fine needle, and had it accurately 

 balanced, so as to turn like a compass-needle with the slightest 

 force. He then placed near the radicle a piece of wood, and 

 covered the whole with a glass, and in process of time the radi- 

 cle was seen to turn directly toward the wood, and that toe 

 without moving the needle; showing that the quantity of mat 

 ter controlled the direction of the radicle, but by the exercise ot 

 no power with which we are acquainted. It could not have 

 been by attraction, for then it would have produced a movement 

 of the needle. It seems to be an exercise of power over the 

 vital energies in producing the turning of the radicle in that 

 direction. The earth no doubt exercises its influence in the 

 same manner. This influence, however, has been counteracted 

 by the application of agents in an unusual manner. Professor 

 SehultZ is said to have succeeded in reversing the growth of 

 plants by planting them in moss, and so arranged tliat the 

 light which they received was the solar rays reflected from a 

 mirror from below upward. Under such circumstances, it is 

 said, the roots take their directions upward, and the stems 

 downward. Similar experiments have not succeeded in the 

 hands of others. 



Notwithstanding such experiments may succeed, we may 

 nevertheless, draw the conclusion, that all roots direct them- 

 selves perpendicularly to the surface of the body on which they 

 naturally germinate ; if they are parasites, they will be perpen- 

 dicular to the surface on which they grow. 



How with seeds in a box ? What the experiment with mistletoe ? How 

 did Shultz reverse the growth of plants? 



