42 



Scientific Proceedings, Royal Dublin Society , 



A study of tlie time-weight curves shows that there is no difEerence 

 in the rate of absorption of seeds, living or dead, in pure water or in salt 

 solutions. Hence one is forced to the conclusion that there is nothing 

 functioning as a semipermeable membrane in the seeds, either living or 

 dead; for if there were, water only would pass in, whereas in reality 

 potassium nitrate solution passes in just as freely. These results are in 

 complete agreement with tliose obtained by A. J. Brown ; for it is only 

 in the special outer covering of Hordenm and some other Glraminese that 

 he finds a semipermeable membrane. Tlius it appears that these seeds do 

 not take up water by the agency of osmotic forces, but solely by capillarity 

 and imbibition, so that tlie material of the dried seed before absorption of 

 water is complete must be in quite a different condition from that which it 

 is in when germination begins and the cells resume their active life. 



Density Determinations. — It was noticed that beans placed in potassium 

 nitrate solution sank, but rose to the surface subsequently, and then, after an 

 hour or more, sank. At first it was suspected that this was due to the 

 expansion of the seed caused by the absorption of pure or less saline water, 

 its density being thus brought below that of the salt solution. Tiiis was 

 completely disproved by a determination of the density and weight of a seed, 

 apparent and real, in pure water. 



Thus it is clear that the rising to the surface of the bean in the salt solution 

 was due to the apparent weight falling to 86 per cent., and the sinking due 

 to its rising to 138 per cent., whereas the density decreased throughout. 

 The crinkling of the coat changes the apparent weight. Beans in a moist 

 place may become so crinkled as to float in pure water. Another air-dried 

 bean used had the initial density of 1-287. Its apparent weight decreased to 



