GERMINATION AND GROWTH OF THE SEED. 21 



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 unat- 

 tended by a perceptible increase of substance, but do- 

 pends 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 ele- 

 ments 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 rela- 

 tion 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 the 

 young plant, the amylum and the nitrogenous and min- 

 eral 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 

 dark, dry, and warm, where the atmosphere was seldom 

 changed was found to have produced, from each bud, 

 a simple white shoot many feet long, showing no traces 

 of leaves, but covered with hundreds of minute potatoes, 

 which exhibited the same internal structure as tubers 

 grown in a field ; the cells consisted of cellulose, and 

 were filled with minute starch granules. It is certain 

 that the starch of the mother tuber, to have moved 

 away from its position, must have become soluble ; but 

 it is equally clear that in the developement of the 

 shoots a cause was operative within them, which (in the 

 absence of all outward causes whereon growth depends) 

 reconverted the dissolved constituents of the mother 

 tuber into cellulose and starch granules. 



