62 



STUDIES IN SEEDS AND FRUITS 



The relation 

 between im- 

 permeability 

 and 

 longevity. 



since a very large amount of interesting, if subsidiary, matter 

 finds no expression either in the table or in the text. 



Professor Ewart arrives at the conclusion that " macrobiotic " 

 seeds (as he terms seeds that may last from 15 to over 100 

 years) are characterised by " more or less impermeable coats, 

 and are restricted to a few natural orders, of which the 

 Leguminosae greatly surpass all others, whilst Malvaceae 

 and Myrtaceae come next in importance." The general 

 trend of the curves, he remarks, indicates that the extreme 

 duration of vitality, probable for any known seed, lies between 

 150 and 250 years. The number of species in the list of 

 plants characterised by macrobiotic seeds amounts to 180, 

 which is less than I per cent, of the total number of species 

 experimented upon ; and of these about 75 per cent, are 

 leguminous. Sixty per cent, or 30 out of the 50 species of 

 Acacia included in the general table possess these long-lived 

 seeds ; and since impermeability and longevity are so closely 

 associated in this genus, we may recall here the high average 

 of impermeability assigned above to seeds of species of Acacia 

 from data supplied in Dr Cola's tabulated results. There 

 is naturally no attempt here to deal with the general question 

 of impermeability, except in its relation to longevity ; and the 

 method of stating the results in the table rarely allows me 

 to draw such inferences for myself with security. Still, some 

 general principles of much importance are indicated in the 

 text and in the table ; and they may be here alluded to. 



In the first place, as was previously implied by Mr Crocker, 

 the impermeability of seeds to water exhibits itself as an 

 adaptation for ensuring the long life of the seed in the soil. 

 It is not essential for securing the longevity of seeds in air. 

 Professor Ewart points out that some seeds with readily per- 

 meable coats, such as those of species of Phaseolus and Triticum^ 

 may retain their vitality for many years in dry air. This 

 being the case, it follows that the experiments, based as they 

 chiefly are on seeds that have been kept in dry air for a 

 varying number of years, are mainly concerned with the 



