200 PHYSIOLOGY OF NUTRITION 



from the soil. Much water escapes from ordinary plants by transpiration, some by 

 guttation, glandular secretion, etc. 



13. Germination of Seeds.— The resting seed contains all the substances needed 

 for a considerable amount of growth, excepting water and oxygen; the latter substances 

 are absorbed as germination starts and proceeds. The earlier stages of germination, 

 until the photosynthesis of carbohydrates becomes pronounced, result in the using up 

 of the non-aqueous materials of the seed; thus the dry weight of a young seedling is 

 smaller than that of the ungerminated seed. 



The chemical processes of germination are different in different kinds of seeds. 

 Seeds may be grouped into three classes according to the substances that predominate 

 in them: starchy seeds, proteinaceous seeds, and fatty seeds. In starchy seeds (such as 

 the cereal grains) carbon, hydrogen, and oxygen are lost during germination. Ger- 

 minating proteinaceous seeds (such as those of the legumes) also give off carbon, hydro- 

 gen, and oxygen, but they are specially characterized by the production of asparagin, 

 amino acids, and some sulphates. Fatty seeds (such as those of sunflower) do not lose 

 oxygen during germination; the oxygen content actually increases. The original 

 supply of fats is depleted and carbohydrates appear, these being apparently formed by 

 the oxidation of the fats. Free fatty acids increase in amount. 



