GERMINATION AND GROWTH 39 



water chinquapin (Nelumbo) have germinated after more 

 than a hundred years, and moss sp'bres preserved in her- 

 bariums, after fifty. But the records in such cases are not 

 always trustworthy, and there is absolutely no foundation 

 for the statements sometimes made about the germination 

 of wheat grains found preserved with mummies over two 

 thousand years old. If kept perfectly dry, however, seed 

 may sometimes be preserved for months, or even years. 

 Peas have been known to sprout after ten years, red clover 

 after twelve, and tobacco after twenty. Ordinarily, however, 

 the vitality of seeds diminishes with age, and in making ex- 

 periments it is best to select fresh ones. Those used for 

 comparison should also, as far as possible, be of the same size 

 and weight. 



35. Effect of precocious germination. It has been found 

 by experiment that plants raised from immature seed, when 

 they will germinate at all (Exp. 32), yield earlier and larger 

 crops than the same kinds from mature seed. Early toma- 

 toes and some other vegetables are produced in this way. 

 The majority of seeds, however, require a period of rest 

 before beginning their life work. Those that are forced to 

 take up the burden of " child labor " show the effect of 

 such abnormal condition by yielding fruits that are smaller 

 and less firm than those raised from mature seed, so that 

 they do not keep well and have to be marketed quickly. 

 Under what circumstances does it pay to cultivate such 

 fruits? 



Practical Questions 



1. What are the principal external conditions that affect germination? 

 (Exps. 26-29.) 



2. What effect has cold? want of air? too much water? 



3. Is light necessary to germination ? 



4. What is the use of clipping seeds ? (Exps. 12, 13, 14, and Material, 

 p. 12.) 



5. In what cases should it be resorted to ? (Exp. 31.) 



6. Why will seed not germinate in hard, sun-baked land without 



