Longevity of Seeds. 186 



adhesive seeds or fruits are conspicuously al)sent anion<r them. 

 They are, in fact, distributed in time instead of in space. Fall- 

 ing to tho gi'ouud beneath or close to the parent plant, a few 

 are immediately germinable, but others only after long periods 

 of yt^ars or after s])ecial actions have been brought to bear upon 

 tliem. 



Although a few seeds (Phaseolus, Triticuni, etc.) with readily 

 permeable coats may retain their vitality for many years in 

 dry air, true macrobiotic seeds, adapted for prolonged duration 

 in the soil, are always possessed of more or less impermeable 

 coats, and they do not swell and germinate until these ooats 

 have been softened. Hiltner- was the first to show that 

 hard clover seeds swelled readily after treatment with strong 

 sulphuric acid, and this observation was extended and confirmed 

 by Jarzymowski.'^ who showed that after appropriate treatment 

 with strong sulphuric acid, followed by washing and neutraliza- 

 tion with dilute amm<mia or lime water, the percentage of clover 

 seed germinating was higher than by any other form of treat- 

 ment, liergtheil and Day^ then found that the hardness of the 

 seeds of Indigofera arrecta was due to the presence of ai very 

 thin impermeable cuticle on the surface of the seed, and that 

 when this was eaten away by half an hour's treatment with 

 strong sulphuric acid, or broken, the seeds swelled readily. 

 Miss White has investigated all the hard seeds, for which I found 

 treatment with sulphuric acid necessary to bring about germina- 

 tion, and has detected in practically all such cases the presence 

 of a cuticle of variable thickness. Her results are added to this 

 paper in the form of an appendix. 



Only in very few cases are seeds which do not absorb water 

 except after filing or special treatment, not provided with a 

 cuticle. One exception is afforded by Adansonia digitata, in 

 which the whole integument seems to be permeable to water with 

 difficulty. In almost all other cases anj^ scratch deep enough to 

 penetrate the cuticle allows the seed to absorb water and swell, 

 and frequently the cuticle then frills or peels off as a transparent 

 membrane. Hard seeds soaked in water for a day or so and then 



1 Arb. au8 der biol. Abt. f. Land, and P'orst. wissensebaft, bd. iii., s. .30, 1902, Berlin. 



2 Inaug. Diss. Halle, 190.i. 



3 Annals of Botany, vol. xxi., .Jan., 1907. 



