CHAPTER TWENTY-EIGHT 

 DORMANCY AND GERMINATION OF SEEDS 



Although the embryo is made up almost wholly of meriste- 

 matic tissue, seeds do not usually germinate as soon as they are 

 mature. In nature only a very small percentage of embryos 

 germinate and grow to maturity ; most of them either fail to 

 germinate, or they perish in the seedling stage. 



Dormancy. When a seed does not germinate immediately 

 after leaving the parent plant, it is spoken of as being in a state 

 of dormancy. The seeds of most wild plants do not germinate 

 immediately after ripening, even though external conditions are 

 favorable. The seeds of many cultivated plants, on the other 

 hand, have little or no dormancy and will germinate during wet 

 weather even before they leave the parent plant. Corn germi- 

 nating in the ear, and wheat and oats sprouting in the shock, are 

 common occurrences in extremely wet weather. The lack of 

 dormancy in seeds of cultivated plants is due, in part, to the fact 

 that man has unconsciously selected those seeds that germinate 

 readily. Obviously, only those seeds that germinate soon after 

 sowing produce mature seeds at harvest time. In the long his- 

 tory of agriculture those individuals and races of plants whose 

 seeds did not germinate readily were largely eliminated. 



An interesting example of the difference in dormancy be- 

 tween wild and cultivated species may be seen in the Dakotas. 

 The common oats and wild European oats both occur and produce 

 seeds in summer. The cultivated oats, however, germinate in 

 early autumn and the seedKngs freeze and die during the cold 

 winter. The seeds of wild oats do not germinate until spring, 

 and consequently they become troublesome weeds in grain fields. 



Sometimes the period of dormancy is very short, as in the seeds 

 of willow, elm, cottonwood, and other spring-fruiting trees. 

 Seeds of this type do not withstand drying and consequently 

 never germinate unless they fall in a moist habitat. The soft 



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