REPRODUCTIVENESS AND SEED GERMINATION 393 



activity of the seed and a return to the dormant state. Removing 

 the membranes (testa or integuments) also removes the dormancy. 

 Viability of Seeds. — The viability or the length of time during 

 which seeds retain their vitality and germinative power is ex- 

 tremely variable. Aside from the influence of external conditions, 

 the specific differences are very great. Some kinds will keep their 

 vitality for only a single season while others will germinate after 

 many years. Under favorable conditions the following durations 

 of viability have been found : 



Seed Years Seed Years 



Alfalfa 8 Onion 5 



Asparagus 5 Peas 3 



Beans 3 Pumpkin 5 



Cabbage 5 Radish 5 



Cereals (wheat, oats, etc.) 8 Red clover 8 



Clover 2 Rice 3 



Corn 2 Squash 5 



Cucumbers 10 Timothy 6 



Geranium 10 Tomato 4 



Lettuce 5 



These figures do not indicate that all the seeds have lost their 

 viability at this time but only that the germination percentage is 

 not high enough after this period to justify their use as seed. 

 Certain seeds (e. g., Geranium) are known to have retained their 

 vitality from 50 to 100 years. If one computes from the percent- 

 age curves the time it would take for every seed to lose its via- 

 bility, some seeds would be found to retain their germinative power 

 150-200 years, but there is no authentic record of any kind of 

 seed which has retained its vitality longer than this period. 



Viable seeds of Nelumbium nucifera (Indian lotus) were re- 

 ported by Ohga to have been found in peat layers at such a depth 

 where they must have been buried for 300-400 years, but seeds 

 from the British Museum would npt germinate when 215 years 

 old, and later it was decided that the deposits in which these seeds 

 were found might be no older than 150-200 years (Ohga, 1927). 

 The stories of seeds from Egyptian tombs and similar places which 

 have germinated after the lapse of centuries, are absolutely with- 

 out foundation. 



The causes of the loss of seed viability are (1) degeneration of 

 the enzymes, (2) accumulation of toxic metabolic materials as 

 the result of the slow katabolism that has been taking place, 

 (3) exhaustion of food reserves, and (4) denaturation of the col- 



