62 ACIDS AND ALKALIES. 



for animals. But the air does not furnish the required quantity. 

 Herbs may grow without it, but no grain ; even starch and sugar may 

 be formed, but no gluten; and plants may produce but one seed to per- 

 petuate their kind. An additional quantity enables the plant to attract 

 more carbon from the air and to fix it in its organization. The gene- 

 ration of organic acids is prevented in all vegetables which yield food 

 to man and animals when alkalies are absent from the soil they grow 

 in. These acids are rarely free, but are found in combination with 

 potash, lime, soda or magnesia, as salts, and as before mentioned. 

 These are not found in all plants. Soda is the only salt in saline 

 plants ; lime and potash form constituents of grain plants. Some have 

 soda and potash, others potash and magnesia ; and the acids vary in 

 a similar manner. The philosophy of cultivation is therefore to give 

 to one plant those substances necessary for its development and to 

 spare those not necessary. Hence the same kind of manure is by 

 no means to be administered to all plants. One may flourish luxuri- 

 antly on an arid soil, while another requires much moisture and dif- 

 ferent quantities at different times. Culinary vegetables contain 

 sulphur, as turnips, rape, cabbage, celery, etc. ; hence they thrive best 

 in soils containing sulphates. This, then, must be introduced where it is 

 not, by urine with gypsum, by wool, horn and hoofs. The best manure 

 for wheat is the ashes of straw. Indian corn, poppies, etc., contain 

 little or no potash. Charcoal is found to be of the greatest importance 

 in the cultivation of plants, and especially animal charcoal. 



Hydrogen is most abundant when plants begin to secrete oils, 

 camphors, etc., which most abound in the tropical plants, from the in- 

 fluence of the sun. The greater sweetness of sub-acid fruits in 

 those than in plants of colder climates arises from the transformation 

 of more tartaric and other acids into sugar in warm climates. This 

 transformation of substances into the organs of a plant is analogous 

 with that of animals ; for the plant must Lave appeared above ground 

 having previously had all the required elements of its growth to 

 that state in its seed. In the early stage of man's existence, before 

 the organs, like those of plants, have acquired the power to effect this 

 transformation and assimilation, he is provided by his mother's milk 

 with the aliment already, or nearly, elaborated as in seeds. 



Leguminous plants, sich as beans, peas, etc. best succeed crops of grain, 

 as they contain no free alkalies required and withdrawn by crops of corn. 

 The same plant differs in constitution when grown in different climates. 

 Thus in the warm climates of France, nitre takes the place of sugar 

 in beet roots. These are thus better for cows, as they require more 

 nitrogen and phosphate of lime for the formation of their milk than 

 sheep, which require more sulphur and salt than they, for the forma- 

 tion of their wool. As all kinds of corn contain nitrogen, a full sup- 

 ply of the materials affording it is of great importance to man. 



