SECT. IV. DECOMPOSITE ORGANS. 247 



The original direction of the root is generally Its direc- 

 perpendicular, in which it descends to a consider- ll< 

 able depth if not interrupted by some obstacle. In 

 taking up some young Oak-trees that had been 

 planted in a poor soil, Du Hamel found that the 

 root had descended almost four feet, while the 

 height of the trunk was not more than six inches. 

 If the root meets with an obstacle it then takes a 

 horizontal direction, not by the bending of the 

 original shoot, but by the sending out of lateral 

 shoots. The same effect also follows if the ex- 

 tremity of the root is cut off. It grows in length no 

 longer. Du Hamel made some Cherry-stones, 

 Almonds, and Acorns to germinate in wet sponges ; 

 and when the roots had grown to the length of two 

 inches, he then placed them in glasses as bulbous 

 roots are placed, so as that the extremity of the root 

 only touched the water. Some were previously 

 shortened by the cutting off of a small bit from the 

 point ; others were put in entire. The former im- 

 mediately sent out lateral shoots, but elongated no 

 farther in a perpendicular direction; the latter de- 

 scended perpendicularly to the bottom of the glass. 

 He cut off also the tips of some roots vegetating in 

 the earth, and had the same result ; the wound 

 citatrized, and the root sent out lateral divisions. 



When a root ceases of its own accord to elongate, Lateral 

 it sends out also lateral fibres, though less vigorously fibrcs 

 and with less rapidity than in the above cases. 

 The lateral branches of perpendicular roots are 



