GROWTH OF PLANTS IN CLOSED GLASS VESSELS. 507 
to have reached the lowest degree of aerial circulation under 
_ which plants will continue to live and thrive, although even this 
_ slow transmission of air was sufficient to their vitality, render- 
ing it only less vigorous and healthy. 
_ To ascertain then what the degree of circulation through the 
substance of the membrane in these instances might have been, 
I removed from one of the jars the plants and vegetable mould 
_ it had contained, and substituted for them about an equal amount 
_ of drysand. I then passed through the vessel a current of oxy- 
_ gen until the volume of air within contained no less than 77 per 
- eent. of that gas. The air was then examined again at 4 p.m., 
after an interval of three hours from the period of the first ex- 
periment, and found to have lost 4 per cent. of oxygen. The 
_ jar was then put aside till eight o’clock the next morning, when 
_ it was found to contain only 63 per cent. of oxygen, having di- 
_ minished in 16 hours 10 per cent. After having been exposed 
all day to air and light, and examined at eight the same even- 
ing, the oxygen was found to amount to.only 46 per cent., having 
_ diminished in 12 hours 18 per cent. During the next night it 
had diminished in 12 hours only 64 per cent., the amount of oxy- 
gen existing in it the next morning being 383 per cent. During 
_ the next day it had lost 7 per cent., containing at eight in the 
evening 31} per cent. The next night the diminution was only 
_ 24 per cent., and on the succeeding day 3 percent. The fol- 
_ lowing night the diminution was 14 per cent., the amount of 
_ oxygen being 24} per cent. only. During the day a further 
diminution of 3} per cent. took place, the air inclosed within 
the jar being found to contain exactly the quantity of oxygen 
_ present in atmospheric air. 
The following is a tabular view of the results :— 
June 23rd 1 p.m. amount of oxygen 77° excess 56° 
a eee 3° 
4 p.m. 52 
24th 8 a.m. —_—_ 63° —— 42: 
8 p.m. ——_- 455 —— 24: 
25th 8 a.m. —_— 38°5 —— 17:5 
8 p.m. —_—__ 31°55 —— 10°5 
26th § a.m. —_——_—_— 29:0 —— 80 
8 p.m. —______- 26°0 — 5:0 
27th 8 a.m. ——__<— 2445 —— 3°5 
8 p.m. a 21°0 0:0 
Thus five days were required to enable the whole excess of oxy- 
_ gen to pass through the substance of the membrane, the dia- 
-Ineter of which was 3 inches, whilst the capacity of the vessel, 
when the sand had been introduced, was nearly one gallon, so 
_ that about three quarts of oxygen and one of nitrogen may be 
