Lonr/fvlfy of Scrds. 199 



(A. dealhata, lon(/i folia). Such seeds when preserved in a dry 

 atmosphere seem to steadily lose water until ultimately as dry 

 as if kept in a desiccator. It is as though the cuticle allowed 

 traces of water to escape externally, but none to enter. Thus 

 fresh air-dried Acacia seed contained 5 to 14 per cent, of mois- 

 ture, whereas 10 to 20-year-old seed of A. myrtifolia. A. longi- 

 folia, A. arDtata and A. chalhata contained only frnm 0.9 to 3.2 

 per cent., and 50-year-old seed of A. myrtifolia and A. longi- 

 folia, after heating to 100 deg. C. for half an hour to drive oflf 

 adherent moisture, lost no further weight after 3 days at 100 

 deg. C, and only 0.7 per cent, after 1 day at 110 deg. C. Fine 

 capillary glass tubes show a greater loss of weight than this, 

 owing to the adherence of condensed moisture, more especially 

 to their internal surfaces. Hence old dry cuticularized macro- 

 biotic seeds become drier than corresponding inorganic material. 

 However dry the seeds may be, they cannot indefinitely prolong 

 their vitality. Even the most resistant seeds after 50 to 100 

 years .sliow a pronounced decrease in the percentage germination, 

 and the general trend of the curves is such as to show that the 

 probable extreme duration of vitality for anv known seed may 

 be set between 150 and 250 years (Leguminosae). Probably the 

 maximal duration for Malvaceae and Nympheaceae lies between 

 50 and 150 years, while for Myrtaceae and the orders containing 

 only one or two macrobiutic seeds it is doubtful whether the 

 limit appreciably exceeds 50 years. Even when perfectly inert 

 a macrobiotic seed is subject to slow and gradual molecular 

 changes and rearrangements, such as take place in glass or wood 

 in the pro-jfross of centuries, and these changes cannot take place 

 in the contents of the seed without destroying the molecular 

 an'anfrements and groupings requisite for the restoration of life 

 Once this has taken place no ferment, no physical or chemical 

 condition can bring about germination. 



General Summary of Tabulated Results.— For purposes of 

 convenience we may divide seeds into 3 biologicfil classes, accord- 

 ing to their duration of life under optimal conditions. These 

 are short lived or microbiotic seeds whose duration does not 

 exceed 3 years, mesobiotic seeds which may last 3 to 15 years, 

 and MACROBIOTIC seeds which may last from 15 to over 100 years. 

 The first two are the more numerous groups, and the boundary 



