GERMINATION AND GROWTH OF THE SEED. 3 



glass plate furnished with fine perforations, through which 

 the roots may reach the water, the grain will go on grow- 

 ing for several weeks without receiving any incombustible 

 element of food or any constituent of the soil. After three 

 or four weeks the apex of the first leaf is seen to turn 

 yellow ; and upon examining the seed, nothing but an 

 empty skin is found, for the starch has disappeared to- 

 gether with the cellulose (]\Iitscherlich). However, the 

 plant does not die away, but new leaves are produced, 

 often also a feeble stalk ; the constituents of the first- 

 formed, but now withering, leaves being applied to the 

 formation of fresh shoots. 



Under favourable circumstances, seeds with very large 

 and vigorous cotyledons abounding in nutritive matter 

 (e. g. beans) may, by vegetation in water alone, be got to 

 flower — nay, even actually to produce small seeds ; this 

 developement, however, is mostly unattended by a per- 

 ceptible increase of substance, but depends solely upon a 

 mere transposition of the elements of the seed. 



Nutrition is a process by which food is assimilated ; a 

 plant grows when its mass is augmented, and its mass 

 is increased by absorbing materials from without, which 

 are, from their nature, suited to become constituent 

 elements of the body of the plant, and to sustain those 

 functions upon which their assimilation depends. 



The bud on a potato-tuber stands in the same relation 

 to the constituents of the tuber as the germ in a corn- 

 seed does to the farinaceous matter of the albumen. 

 While the bud is developed in the formation of tlie 

 young plant, the amylum and the nitrogenous and 

 mineral constituents of the sap of the tuber are employed 

 to form the young branches and leaves. A potato, 

 which lay wrapt up in thick paper, in a box, in the 

 Chemical Laboratory at Giessen — in a place absolutely 



b2 



