392 Plant Physiology 



came to my attention in Columbia, Mo., of the germina- 

 tion of clover seed which had been buried for more than 

 thirty years. The conditions were these : A cut was made 

 in clay soil exposing the ground-level of a fill made more 

 than thirty years before of from two to four feet. A few 

 weeks after the exposure of the old ground-level a contin- 

 uous growth of white clover appeared along that line. 

 There could be no doubt of the age of those seed, and an ex- 

 amination of undisturbed soil farther in disclosed the fact 

 that there were present not only white and red clover 

 seed capable of germination, but also, in smaller quantity, 

 cocklebur, sonchus, and a species of sedge. 



In general, it would seem that the burial of agricultural 

 seeds results in death far more promptly than in the case 

 of resistant weed seeds. Shallow burial of weed seeds, 

 however, affording moisture conditions favorable for 

 decay, may often result in their destruction. 



233. Delayed germination. The rest period of the 

 seed seems to be to a considerable extent, if not entirely, 

 due to the development of a structure, or device, during 

 the maturing process which may serve to exclude water 

 or air until acted upon by gradual processes of decay or 

 special agents. It is well known that the germination of 

 many seeds is quickened by soaking in strong sulfuric 

 acid, by cracking the tough seed-coats, and some even by 

 the action of the digestive juices of certain animals. 



Nobbe and others have pointed out the relation of 

 germination to certain structural devices. Recently 

 Crocker finds that the marked case of delayed germina- 

 tion in the seed of Abutilon is due to the fact that the 

 condition of the seed-coats precludes the possibility of 



