PROCEEDINGS OF THE FARMERS' CLUB. • 325 



food from tlie soil, they mutually injure each other, -Therefore 

 it is not wonderful that wild chamomile impedes the growth of 

 €orn, when it is remembered that both yield seven per cent, of 

 ashes, which contain six-:tenths of carbonate of potash. 



Plants, on the other hand, will thrive next to each other when 

 the matters necessary for their growth, which they imbibe from 

 the soil, are of different kinds, or when they are not in the same 

 stage of development at the same time. 



On a soil, for instance, in which potash abounds, tobacco and 

 wheat may be grown in succession, because the tobacco does not 

 require the phosphates — which are indispensable to wheat — but 

 the alkalies and food containing nitrogen. 



According to the analysis of Possett and Riemann, 10,000 parts 

 of the leaves of the tobacco plant contain only sixteen parts of 

 phosphate of lime, eight parts of silica and no magnesia ', while 

 an equal quantity of wheat straw contains forty-seven parts, and 

 the same quantity of the grain of wheat ninety-nine parts of the 

 phosphates. This is a very considerable difference. 



The roots of plants collect these alkalies from the rain which 

 formed part of the sea water, as well as those of the water of 

 springs, which penetrate the earth. Without alkalies and alka- 

 line bases most plants could not live, and without plants the 

 alkalies would gradually and surely disappear from the surface 

 of the earth. When it is remembered that sea water contains 

 one-millionth of its own weight of iodine, and that iodine in all 

 its combinations with alkalies is soluble in water, some provision 

 must exist in the organization of sea weed and fuci, by which 

 they are enabled to extract iodine from sea water, and to assim- 

 ilate it in such a remarkable manner, that it is not quite restored 

 to the surrounding medium. 



This family of plants are collectors of iodine, precisely as land 

 plants are of alkalies, and they afford us this element in quanti- 

 ties that we could not otherwise obtain except by the evaporation 

 of the whole ocean- 

 No man living knows what strength and height is allotted to 

 any plant by nature. I have seen oaks grown by Chinese gar- 

 deners fourteen inches high, the whole habitus of which evinced 

 an advanced age. 



I was particularly struck with this fact a few years since, 

 when a friend of mine presented me with some seeds of the 

 Teltow turnip, which he purchased in a village of that name 



