ENERGY OF IMBIBITION 177 



should be wound once around the rim of the bulb and the ends 

 twisted with a pair of pincers. Hold the bulb in the center of 

 the jar and pour seeds of pea, bean, or soja bean, around it until 

 the jar is completely filled. The seeds should be compacted by 

 shaking from time to time. Now bring the top to its place and 

 screw on. Set the jar in a larger vessel with the manometer arm 

 extending above and outside it. Pour water in the vessel in such 

 manner that it will completely cover the jar containing the seeds. 

 Mark the exact height of the mercury in both columns, and adjust 

 the outer arm to a perpendicular position. Measure accurately 

 the length of the column of air above the mercury in the enclosed 

 column. As the seeds in the jar swell, the bulb will be compressed 

 and the mercury driven up in the outer arm of the manometer. 

 Note the length of time elapsing before imbibition begins, as de- 

 noted by the rise of the mercury column, and measure the length 

 of the column of air at intervals for a day. Part of the effect will 

 be due to the osmotic power of substances in the living cells. 

 The actual amount of pressure is to be calculated by Boyle's 

 law. The volume of a gas varies inversely with its pressure. 

 Thus if the column of air originally measured 8 cm. and is com- 

 pressed to 6 cm. in length the pressure will be eight-sixths of 

 an atmosphere l (Fig. 84). 



An iron cylinder was filled with peas and fitted as in Fig. 84, 

 on February 23, 1901, and the following observations made : 



Time. Length of Column of Air. 



9:30 A. M. 6.30 cm. 



10:00 " 5.90 " 



10:06 " 5.50 " 



10:10 " 5.20 " 



10:35 " 4.60 " 



10:42 " 4.30 " 



10:51 " 4.10 " 



ll:ll " 3.80 " 



11:40 " 3.40 " 



11:50 " 3.20 " 



1 Coupin, H. Recherches sur 1'absorption et le rejet de 1'eau, par les graines. 

 Ann. Sc. Nat. Bot. 8. 2 : 128. 1895. 

 13 



