98 GERMINATION OF SEEDS: SEEDLINGS 



during a germinative period of only 48 hours. That moisture 

 is liberated during germination is obvious, for the air in a closed 

 germinator often becomes so saturated that moisture precipitates 

 on the walls of the germinator. 



When green seeds, green hay, or any plant portions in which 

 the cells are quite active are massed together, so that the heat and 

 moisture are retained, they often become very warm and moist 

 due partly to their own respiration and partly to that of the micro- 

 organisms present. The so-called "sweating" of grains in the 

 stack or bin and the heating in the bin when the grain becomes 

 damp due to leaks are phenomena connected with respiration. 



Summary. — In germination of seeds the following things take 

 place: (1) the absorption of water which softens the seed cover- 

 ings and acts as a dissolving and transporting medium of foods ; 

 (2) the secretion of enzymes which digest the foods and assist in 

 other processes; (3) the transference of foods by diffusion and 

 osmosis; (4) respiration which supplies energy for the elabora- 

 tion of foods into plant structures and is accompanied by the ab- 

 sorption of oxygen and the production of carbon dioxide, water 

 vapor, and some heat; and (5) the growth of the radicle and 

 plumule, resulting in the breaking of the seed coverings and the 

 establishment of the young plant in the soil and sunlight. 



Testing the Germinative Capacity of Seeds 



The loss in crop and labor when poor seed is used may be so 

 serious that no one can afford to plant seeds with a doubtful ger- 

 minative capacity. It is not enough for seeds to germinate, but 

 they should have vigorous embryos, so that they will germinate 

 quickly and thus rapidly pass through the delicate stage in which 

 the young plant is likely to be destroyed by insects, Fungi, bad 

 weather, and unfavorable soil conditions. 



In testing the germinative capacity, as in determining the im- 

 purities of a quantity of seeds, decision is based upon the results 

 obtained with a comparatively small number of the seeds as a 

 sample. In case of small seeds, such as Oats, Wheat, Barley, and 

 Clover, Alfalfa, and Grass seeds, tests are ordinarily made with 

 two lots consisting of 200 seeds each and free from impurities. 

 In Corn it is customary to use 6 kernels, 2 from near the tip, 

 2 from the butt, and 2 from the middle of the ear, with the 

 kernels of each pair selected from rows as far apart as possible. 



