464 Scientific Proceedings, Royal Dublin Society. 



screwed on. In the centre of the mass of seeds he placed a bag containing 

 liquid, which was connected by a tube witli a pressure-gauge, indicating 

 pressures on a dial. 



Water was admitted by a second tube entering the mass of seeds. The 

 figures were variable even with the same species of seed. 



His experiments were repeated by Coupin (4), who states : " Les ehiffres 

 obtenus par M. Grrehant sont variables avec uue meme espece de grains. J'ai 

 repet^ quelques-unes des experiences de M. Grehant, et j'ai trouve des 

 resultats non moins variables. A cet egard, on ne pent donner aucun cliiffre 

 absolu : tout ce qu'on peut dire, c'est que certaines semences, celles de 

 Lupin blanc, par exemple, donnent des pressions plus fortes que d'autres, 

 telles que celles de Mais, par exemple. 



" La variabilite des resultats obtenus ne doit pas d'ailleurs nous 

 etonner, car cette pression depend de la position des graines les unes par 

 rapport aux autres et des vides qu'elles laissent entre elies." 



Coupin observes that the maximum pressure is not obtained, since the 

 seeds near the orifice of the water-inlet tube swell rapidly, and close the 

 opening, thereby stopping the further supply to the main mass of seeds. 



Eeguard (12) criticizes these experiments of Grehant on similar grounds. 

 Macdougal (11) used an apparatus similar to that of Grehant, but admitted 

 the water through holes in the metal cover. He placed a rubber bag 

 containing water in the centre of the seeds. This bag was connected by a 

 glass tube with an air manometer containing water and mercury. 



" The total duration of tlie experiment was 30 hours, and the final 

 pressure attained was sufficient to compress a column of air from a length 

 of 6-30 to -78, and tlie amount is indicated as 630/78 = 8 atmospheres or 

 120 pounds to the square inch. This pressure was maintained for two days, 

 and then began to decrease slowly, showing but 1'2 atmospheres a week later, 

 or 18 pounds to the square inch." 



We have often noticed a slight falling off of pressure after the maximum 

 was reached, but in some cases pressures of over 25 atmospheres were 

 maintained for prolonged periods — once for over six months. Whenever the 

 pressure dropped to any groat extent, subsequent examination proved the 

 existence of a leak, which was easily detected, as we used mercury. 



Macdougal's lower I'esults may have been also due to leaks ; but as the 

 rubber bag in his experiment contained water, the leak wou.ld not be detected 

 so easily. 



Coupin studied especially the quantity of water absorbed by seeds under 

 varying conditions. His results may be briefly summarized as follows : — 



The total water absorbed by dead or anaesthetised seeds is the same as 



