CH. II.] THE ROOT. 97 



becomes putrescent ; the remainder is chiefly phos- 

 phate and carbonate of lime, salts which are com- 

 ponents of wheat, r}'e, barley, oats, peas, beans, 

 vines, cucumbers, potatoes, garlic, onions, truffles, &c. 

 Common salt, also, is employed as a manure, and is 

 beneficial, partly in consequence of entering into the 

 constitution of plants. 



The day has long passed when it was disputed 

 whether saline bodies ai-e promotive of the gro\^1:h 

 of plants. It is now deteiTained that some plants 

 will not even live without the means of pro- 

 curing certain salts. Borage, the nettle, and parie- 

 taria will not exist except where nitrate of potash is 

 in the soil ; turnips, lucerne, and some other plants V 

 will not succeed where there is no sulphate of lime. 

 These are facts that have silenced disputation. Still 

 there are found persons who maintain that salts are 

 not essential parts of a plant's stiiicture : they assert 

 that such bodies are beneficial to a plant by absorb- 

 ing moisture to the \icinity of its roots ; or by 

 improving the staple of the soil ; or by some other 

 secondar}' mode. This, however, is refuted by the 

 fact that salts enter as ultimately into the con- 

 stitution of plants as do phosphate of lime into 

 that of bones, and carbonate of lime into that of 

 egg-shells. They are part of their very fabric, 

 universally present, remaining after the longest 

 washing, and to be found in the ashes of all and of 



H 



