38 ON MILDEW, OR MELDEW. 
along with it, remains pent up within us, without a possibi- 
lity of escape, to our great suffering and discomfort. 
There are other conditions of the crop, which render the 
above circumstances more certainly fatal, but it is doubted 
whether alone they would be much detrimental in producing 
mildew — such as a very succulent, vigorous growth, produced 
by manuring too highly, &c. 
Now for the theory ; the word I don't like much, because 
farmers in general complain so much about theories ; but have 
them we must, while men continue to think ; for if we think 
about facts, we are constantly forming theories, in spite of our 
wishes to the contrary ; but theories are only bad or wrong 
when they don't explain facts, and of this every man must 
judge for himself. If theories are true and give sound rea- 
sons for things, they are good theories, if not, they are bad, 
and should be discarded without ceremony. 
All plants derive their nutriment from the earth, and take 
it up in a state of very dilute solution in water ; this is elabo- 
rated in their organs, in a way incomprehensible to us, and 
deposited where it is needed, to promote the growth and ex- 
pansion of the plant, and enable it to perform the functions de- 
signed in its creation ; and the great object would seem to be, 
to cause it to perfect its seed and continue its species. When 
this deposit of nutriment is made, the water, which was its 
vehicle of conveyance, is thrown out of the plant as excre- 
mentitious by proper exhaling vessels, and is dispersed in the 
form of vapor, in the atmosphere, and the vessels of cir- 
culation, which are in continual action, introduce continued 
supplies of similar nutriment duly prepared for deposit, and 
throw off the water as before, so that there is never a vacuum 
in the plant. 
This process is in continual action till the plant is perfect- 
ed, and the quantity of water thrown off during the progress 
of vegetation is almost incredible, as would appear by some 
very accurate experiments made to indicate the amount. Of 
15 parts of water taken up by some plants, 13 are transpired, 
and of the lowest on the scale, of 5 parts taken up 4 are dis- 
charged by exhaling vessels. 
