THE SEED 37 



Soundness of a Seed. — Seeds which are not sound, have 

 their vitaHty weakened. The soundness of a seed is influenced 

 by: (1) Injury due to thrashing, (2) by the action of physical 

 or chemical agents, (3) by being imperfect or shrivelled, (4) 

 by being produced from plants that were stunted in their 

 growth either by fungi or insects. All of these phases are 

 harmful to the germination of a seed. It follows, then, from 

 facts well in hand, that seeds which are in any way injured 

 should be discarded, and that soundness should be one of the 

 requisites of a good seed. Unsound seed should be destroyed 

 because weakly and sickly plants will be produced. 



Seed that are eaten or injured by certain insects, such as 

 the pea weevil or bean weevil, produce great loss annually. 

 Plants grown from seed injured in this way are retarded in 

 growth, with the result that weak plants are produced. The 

 amount of damage resulting to seed by the attack of insects 

 is not always in proportion to the part injured. The pea 

 weevil sometimes destroys most of the stored food in the pea, 

 but if the pumule is untouched the pea will germinate. On 

 the other hand, a slight injury to the pumule will destroy the 

 germinating power of the seed even though all of the food 

 material is uninjured. 



Longevity of a Seed. — ^The length of time a seed is alive is 

 called longevity. The longevity of seed is a much-discussed 

 question, although one that can be easily settled, and a 

 question upon which there is much authentic data. The lon- 

 gevity of a seed depends for the most part upon the species, 

 but also differs widely in this respect. The climatic con- 

 ditions materially influence the longevity of a seed and none 

 of the qualities of a seed, such as weight, color or size seem 

 to be correlated in any way with the length of life of the 

 embryo of a seed. Poor method of harvesting, poor storage 

 facilities, mechanical injuries of various kinds, which affect 

 the food supply of the embryo, all tend to shorten the life 

 of the seed, Likewise immature seeds begin to fail earlier 

 and die before their natural time. Improper fertilization or 

 poorly formed and imperfect embryo give short-lived seed. 

 The position of the fruit on the plant sometimes exercises 

 an influence on the germinating power of the seed. 



