500 Experiments &3 Odfervations 
Experiment XV. Six feeds of white muftard 
(Sinapis alba) were planted, about the middle 
of March, in aglafs bottle; the bottom of which 
was covered with moift earth, the upper part 
being occupied with common air. The mouth 
was then well corked, and fecured with cement. 
The young plants pufhed their tips into view 
in the courfe of a few days, and appeared in a 
thriving condition; but began to droop before 
the end of the week, and died in a fhort time 
after. The air was found to be unfit for com- 
buftion. Probably the wet mould confined in 
it contributed not a little towards depriving it of 
its oxygene; for the mud of rivers and ponds has 
been difcovered to poffefs this property i in a 
high degree.. 
The fads related in the two laft satjéhes 
prove, ina clear manner, that feeds which have 
been permitted to grow for a time in the at- 
mofphere, ceafe to do fo when they are fur- 
rounded with azote: whence it may be fafely 
inferred, that a germ in the act of vegetation 
requires to be continually excited by the ftimulus 
of oxygene. But as foon as the feed lobes are 
exhaufted, the young plant is in a ftate to de- 
rive its nutrition from the ground; and then 
(and nottill then) it finds itfelf in afituation capa- 
ble of making future advances; unaflifted "y the 
ftimulus of refpirable air, 
The 
