336 FRUITS AND SEEDS 



taining the developing embryo, grows to a certain size. 

 Upon attaining this size, the outer part of the ovule (integu- 

 ment) develops into the seed coat or testa, and the growth 

 of the young plant within is checked. It is the appearance 

 of the testa which marks the transformation of the ovule 

 into the seed. 



The size of seeds varies exceedingly among different kinds 

 of plants, but it is strikingly uniform in any single species. 

 In fact, in plants of the same kind, no other organs exceed 

 fruits and seeds in uniformity, both as to size and as to 

 structure. 



The size of seeds is significant in connection with germina- 

 tion. If the seed is small and poor in food, the young root 

 must quickly find soil water and the shoot must quickly 

 reach the sunlight. The nursing tissue alone cannot sustain 

 them long. If the seed is large and rich in food, the little 

 plant has a better chance. Yet most plants come from 

 small seeds. Small seeds are much cheaper for the parent 

 to produce and are produced in far greater numbers than 

 large seeds. They are much more successful in dissemina- 

 tion than large seeds are. Their disadvantage as to food 

 supply appears to be more than offset by their advantages 

 in respect to numbers and distribution. 



A . The Importance of Seeds to Mankind. — Think of 

 what seeds mean to men. Think how different human 

 history would be if it had not been for the evolution of the 

 seed habit. It is the nourishment stored in seeds which 

 is our main source of food. The seeds of rice and corn and 

 wheat are the " staff of life " for human beings. And if it 

 were not for seeds, how would the millions of acres of the 

 farms be brought to harvest ? Not only are seeds of great 



