THE PLANTING OF OUR FLORA 159 



requires some time to recover. This irregularity 

 may be due in part to the poverty of the soil, for 

 even our cultivated fruit trees with all the diligent 

 care we give them usually produce more abundant- 

 ly on alternate years. 



If all the seeds from a "bumper crop" germi- 

 nated there would not be room for the little plants 

 to stand and nearly all would die of overcrowding. 

 So the trees seem to resort to an expedient, as do 

 many animals. They apparently use devices 

 which if employed by humans would be attributed 

 to reason. They cannot voluntarily regulate 

 their bearing but they seem able to control their 

 seeds for a time after they have fallen; in other 

 words, they adopt a sort of balance wheel principle 

 in the germination of the fruits to counterbalance 

 the irregularity with which they produce them. 

 So it often comes about that only a few seeds may 

 come up at once and those of a single crop may 

 continue to germinate for a long series of years. 

 This gives them a far better chance, for if all 

 grew at once (granting pleiity of room), a hard 

 freeze, a fire, a drought, floods, insects, or disease 

 might destroy them all. They do not put all 

 their eggs in one basket. 



