HIGHER AND LOWER PLANTS 261 



construct proteids and carbohydrates as we are told our now 

 automatic cousins were once taught to do; though man fails 

 to consider that it may be a lost art, and the secret has died 

 with the plants in a " catagenetic " decline. 



All plants and their products are composed of two general 

 classes of compounds, volatile and fixed. The former, on 

 incineration of the plant, are transformed into gases, leaving 

 the last as so-called ash-constituents. 



I will very briefly refer to the sources of the substances 

 which go to the building of the plant structure. Green plants 

 derive their carbon from the carbon dioxide of the atmosphere, 

 and even from complex organic compounds, since Darwin 1 

 has shown that insectivorous plants, by means of their modified 

 leaves, are able to absorb flies and other small insects. 



Plants that do not contain chlorophyll, as fungi, take 

 their carbon from complex compounds of decaying organic 

 matter. Not only do all the so-called organic compounds of 

 plants contain carbon, but it is found also in the form of car- 

 bonates. 2 



Hydrogen is absorbed by all plants in the form of water, 

 or ammonia and its compounds, or in complex substances, 

 as mentioned above. Oxygen is taken up by plants free or in 

 combination, in water or in salts, and there are six possible 

 sources of nitrogen supply; but I will not delay by going into 

 this subject. 8 



Sulphur and phosphorus are constituents of proteids, and 

 are derived from inorganic compounds. In addition to these 

 the elements essential to the nutrition and maintenance of 

 the life of all plants are potassium, calcium, magnesium, iron 

 in the case of green plants, its absence producing the con- 

 dition of etiolation; and, in certain cases, chlorine. Silicon, 

 fluorine, manganese, sodium, lithium, rubidium, caesium, 

 barium, strontium, aluminium, zinc, copper, arsenic, titanium, 

 iodine, and bromine have also been found among the ash- 

 ingredients of certain plants. 



1 Insectivorous Plants. 2 Ann. Phys. et Chim., Berthelot. 



3 " The Economical Aspect of Agr. Chem.," by H. W. Wiley, Proc. A. A. 

 A. S., vol. xxxv, 1886. 



