28 STUDY OF COMMON PLANTS. 



accompanied by a rise of temperature, and chemical ex- 

 amination indicates absorption of oxygen and exhalation 

 of carbon dioxide ; in other words, respiration is going on. 

 The length of time during which seeds retain their 

 vitality has been the subject of much discussion. Stories, 

 Duration of frequently repeated, of the growth of grain 

 vitality. many centuries old, taken from Egyptian tombs, 

 and of raspberry seeds from a Roman skeleton in England, 

 etc., are generally discredited, for the reason that sufficient 

 proof is lacking. On the other hand, a series of experi- 

 ments, conducted for a long period by a committee of 

 the British Association for the advancement of science, 

 shows that some seeds have certainly retained their ca- 

 pacity for germination from twenty to forty years, and 

 even longer. 1 



1 Report of British Association, 1857, Dublin meeting. 



