CONSTITUENTS OF PLANTS. 



39 



plains grown from the seeds of this contain 

 only salts of potash, with mere traces of 

 muriate of soda. (Cadet.) 



The examples cited above, in which the 

 quantity of oxygen contained in the bases 

 was shown to be the same, lead us to the 

 legitimate conclusion that the developement 

 of certain plants is not retarded by the sub- 

 stitution of the bases contained in them. 

 But it was by no means inferred that any 

 one base could replace all the others which 

 are found in a plant in its normal condition. 

 On the contrary, it is known that certain 

 bases are indispensable for the growth of a 

 plant, and these could not be substituted 

 without injuring its developement. Our in- 

 ference has been drawn from certain plants, 

 which can bear without injury this substitu- 

 tion ; and it can only be extended to those 

 plants which are in the same condition. It 

 will be shown afterwards that corn or vines 

 can only thrive on soils containing potash, 

 and that this alkali is perfectly indispensable 

 to their growth. Experiments have not 

 been sufficiently multiplied so as to enable 

 us to point out in what plants potash or soda 

 may be replaced by lime or magnesia; we 

 are only warranted in affirming that such 

 substitutions are in many cases common. 

 The ashes of various kinds of plants contain 

 very different quantities of alkaline bases, 

 such as potash, soda, lime, or magnesia. 

 When lime exists in the ashes in large pro- 

 portion, the quantity of magnesia is dimi- 

 nished, and in like manner according as the 

 latter increases the lime or potash decreases. 

 In many kinds of ashes not a trace of mag- 

 nesia can be .detected. 



The existence of vegetable alkalies in com- 

 bination with organic acids gives great 

 weight to the opinion that alkaline bases in 

 general are connected with the developement 

 of plants. 



If potatoes are grown where they are not 

 supplied with earth, the magazine of inor- 

 ganic bases, (in cellars, for example,) a true 

 alkali, called Solanin, of very poisonous 

 nature, is formed in the sprouts which ex- 

 tend towards the light, while not the smallest 

 trace of such a substance can be discovered 

 m the roots, herbs, blossoms, or fruits of 

 potatoes grown in fields. (Otto.) In all the 

 species of the Cinchona, kinic acid is found; 

 but the quantity of quinina, cinchonina, and 

 lime, which they contain is most variable. 

 From the fixed bases in the products of in- 

 cineration, however, we may estimate pretty 

 accurately the quantity of the peculiar or- 

 ganic bases. A maximum of the first cor- 

 responds to a minimum of the latter, as 

 must necessarily be the case if they mutually 

 replace one another according to their equi- 

 valents. We know that different kinds of 

 opium contain meconic acid in combination 

 with very different quantities of narcotina, 

 morphia, codeia, &,c., the quantity of one 

 of these alkaloids diminishingon the increase 

 of the others. Thus the smallest quantity 

 of morphia is accompanied by a maximum 



of narcotina. Not a trace of meconic acid* 

 can be discovered in many kinds of opium, 

 but there ib not on tnis account an absence 

 of acid, for the meconic is here replaced by 

 sulphuric acid. Her^, also, we have an ex- 

 ample of what has been before slated, for in 

 those kinds of opium where both these acids 

 exist, they are always found to bear a cer- 

 tain relative proportion to one another. At- 

 tention to these facts must be very important 

 in the selection of soils destined for the cul- 

 tivation of plants which yield the vegetable 

 alkaloids. 



Now if it be found, as appears to be the 

 case in the juice of poppies, that an organic 

 acid may be replaced by an inorganic, with- 

 out impeding the growth of a plant, we must 

 admit the probability of this substitution 

 taking place in a much higher degree in the 

 case of the inorganic bases. 



When roots find their more appropriate 

 base in sufficient quantity, they will take up 

 less of another. 



These phenomena do not show themselves 

 so frequently in cultivated plants, because 

 they are subjected to special external condi- 

 tions for the purpose of the production of 

 particular constituents or particular organs. 



When the soil, in which a white hyacinth 

 is growing in a state of blossom, is sprinkled 

 with the juice of the Phytolacca decandra, 

 the white blossoms assume in one or two 

 hours a red colour, which again disappears 

 after a few days under the influence of sun- 

 shine, and they become white and colourless 

 as before.f The juice in this case evidently 

 enters into all parts of the plant, without 

 being at all changed in its chemical nature, 

 or without its presence being apparently 

 either necessary or injurious. But this con 

 dition is not permanent, and when the bios 

 soms have again become colourless, none 

 of the colouring matter remains ; and if it 

 should occur that any of its elements were 

 adapted for the purposes of nutrition of the 

 plant, then these alone would be retained, 

 whilst the rest would be excreted in an al- 

 tered form by the roots. 



Exactly the same thing must happen 

 when we sprinkle a plant with a solution of 

 chloride of potassium, nitre, or nitrate of 

 strontia; they will enter into the different 

 parts of the p'lant, just as the coloured juice 

 mentioned above, and will be found in its 

 ashes if it should be burnt at this period. 

 Their presence is merely accidental ; but no 

 conclusion can be hence deduced against 

 the necessity of the presence of other bases 

 in plants. The experiments of Macaire- 

 Princep have shown, that plants made to 

 vegetate with their roots in a weak solution 

 of acetate of lead, and then in rain water, 



* Robiquet did not obtain a trace of meconate 

 of lime from 300 Ibs. of opium, whilst in other 

 kinds the quantity was very considerable. Ann. 

 de Chim. liii. p. 425. 



t Biot, in the Comptes rendus des Seances de 

 ['Academic des Sciences, a Paris, ler Semestre, 

 1837, p. 12. 



