42 SEED AND ITS NEEDS 



on account of the temperature deeper than is necessary to 

 secure the proper amount of moisture. 



Processes of Germination. — The processes of germination 

 are divided into five distinct stages : (1) the seed mechanically 

 absorbs water which causes it to swell; (2) the absorption 

 of oxygen; (3) by the absorption of the water and the oxygen 

 the food materials are brought into solution. Some of the 

 food materials as sugars are soluble in the water, while others, 

 such as the oils and the starch must undergo a chemical 

 change before becoming soluble. The oils are thought to 

 pass through several changes, finally being transformed 

 into starch. All of the starches are then acted upon by 

 certain ferments which convert them into soluble carbohy- 

 drates. (4) The soluble food passes to the growing parts of 

 the plant. (5) The food is then employed in the unfolding 

 and the building up of the embryo. After the first two 

 steps the processes go on simultaneously. 



The Internal Conditions Effecting Germination. — In con- 

 sidering germination the internal conditions governing the 

 germination of seed must be emphasized. These are quite 

 as important as the external factors and are four in number: 

 (1) maturity, (2) soundness, (3) viability, and (4) germinative 

 energy. 



The Maturity of a Seed. — The power of germination in a 

 seed is not one of the distinguishing characteristics of the 

 maturity of a seed because many seeds will germinate long 

 before their color, weight, size or shape indicates maturity. 

 Innumerable experiments, as well as many examples seen in 

 the common practice of gardening, have proved that the 

 viability of a seed is not coincident with the maturity but 

 precedes it. Maturity may be summed up by saying that 

 when plants are grown from seed that are immature the 

 following detrimental effects are seen in the plant: (1) there 

 is a loss of vigor shown by the smaller percentage of germina- 

 tion; (2) the weakness of the seedlings; (3) a greater number 

 of plants die before maturity; (4) the full vigor of the plant 

 is never recovered, although it may and usually does produce 

 an abundant harvest; (5) the reproductive parts of the plant 

 are increased in proportion to the vegetative parts. 



