84 ON VEGETABLE PHYSIOLOGY. 



seed, and excites the saccharine fermentation, by 

 which the farinaceous matter is converted into a 

 .sweet emulsion ; while the vessels in the seed 

 begin to expand and ramify in every direction in 

 each lobe from the circumference to the centre, 

 until they terminate in a single tube, forming the 

 channel by which the nutritive fluid is conveyed 

 into the radicle of the embryo plant. The vital 

 principle being thus excited, the gases set at liber- 

 ty by the fermentative process, cause the seed to 

 burst, and the cotyledons to be rent asunder. 

 The radicle now meeting with no opposition, 

 strikes into the ground, and forms the root of the 

 plant ; and sending through its tube, a supply of 

 the newly prepared liquid to the plumula, (pre- 

 viously distended by the heat of the process); the 

 plumula also begins to expand, until it forces its 

 way above the surface, and forms the early stem, 

 carrying with it the cotyledons; which, as soon 

 as they come in contact with the air, spread them- 

 selves laterally, and are converted into leaves, 

 and from this circumstance, they have been 

 termed the seminal or seed leaves. 



Theseleaves continue to supply the young plant 

 with nutriment, until the root has extended itself 

 into numerous ramifications, capable of absorb^ 

 ing nourishment from the ground, and until the 

 upper leaves have been formed ; when the assis- 

 tance of the latter being no longer required, they 

 gradually decay and drop off: the plumula then 



