40 SEED AND ITS NEEDS 



something of the conditions under which the plant producing 

 them grew to maturity. 



Except in the case of soaking, water should not be applied 

 directly to seed but through some medium in which the 

 water can be carefully regulated. The usual media are soils, 

 plant fiber, earthenware and occasionally bricks or tile. 



Seed should not be kept permanently wet, . because in 

 such an event oxygen cannot enter the soil, which, in turn, 

 causes the seed tissue to break down with the formation of 

 alcohol, and later oils and acids, and the seeds are ruined 

 by rotting. It is a safe rule to allow the seed-bed to become 

 quite dry before watering. When watering the whole mass 

 of earth should be completely saturated. It is rarely ever 

 advisable to give a light sprinkling to the surface. The 

 practice of repeatedly wetting the upper surface of the soil 

 is most detrimental. It causes a crust to form and brings 

 the tender roots to the surface, which are later injured by 

 drying out. A watering pot with a fine spray is the best 

 means of applying the water, because the hose usually packs 

 the soil, washes out the seed and makes it difficult to regulate 

 the quantity. 



Oxygen Necessary for Germination. — Oxygen is quite as 

 important to the seed as is water. In the absence of oxygen 

 the food materials in the seed do not pass into solution and 

 do not become available for the young plant. Without 

 oxygen there can be no organic life, and this is as true of 

 plants at this stage as at any other. It has been found that 

 the movement of the protoplasm ceases at once in sprouting 

 seeds if a supply of oxygen is not present, even when the 

 conditions of moisture and temperature are favorable. In 

 the presence of moisture and the absence of oxygen, alcoholic 

 and other fermentations quickly take place. 



In the sowing of seed the aeration of the soil must be taken 

 into account, so there can be an interchange of gases, espe- 

 cially of oxygen and carbonic acid gas. 



The main considerations in securing a supply of oxygen 

 for seed are: (1) Do not drive out all of the oxygen in the 

 crevices of the soil by heavy watering. „(2) Do not cover the 

 seed so deep that it will prevent the easy access of the air. 



