•■iO BIOLOGY. [BOOK r. 



manganese, silicium, chlorg. Finally, in the marine plants we 

 discover iodine and hrome. 



Such are the ultimate results of analysis ; but, of course, 

 during life, these bodies are not, for the most part, in a state of 

 liberty ; they are combined in various manners. The metals are 

 usually in the state of salts, of sulphates, of phosphates, of 

 carbonates, of oxalates, and so on. There is also a certain 

 quantity of oxygen, of azQie, of hydrogen and of carbonic acid 

 dissolved in the liquids or impregnating the vegetal anatomical 

 elements. But the true organic compounds are ternary or 

 quaternary compounds. The ternary compounds are foimed of 

 carbon, of hydrogen, and of oxygen. They constitute the strongest 

 part of the vegetal texture. Let us mention first of all cellulose, 

 which forms almost alone the primary part of the vegetal cells, 

 and then many substances which are isomeric to it, such as in- 

 uline and xylogen. The first of these isomers of cellulose, inuline, 

 is found in decomposed roots, in colchicum bulbs, in dahlia 

 tubers, and so on. As to xylogen, it is the substance which gives 

 rigidity to ligneous tissues. Furthermore, in putting ourselves 

 at the point of view of chemical composition we have to see the 

 relation of cellulose to the starches,' the sugars and the gums. 

 To the type of sugars, the sugar of grape, or glycose, has long 

 been given the formula C^-H'^0^^2H0. Starch is composed of 

 C'^H'C)',HO. In reality, these ternary bodies have already in a 

 large measure the characteristics of complexity and instability 

 peculiar to organic substances, and their definitive formula is 

 still a subject of discord among chemists. According to M. 

 Wurtz, for instance, the formula of cellulose would be C^H^O" 

 that of gum arable Ci^ffW^ that .of starch C H"0^ and this 

 formula would not vary by the isomeric transformation of starch 

 into dextrine. Saccharine and amylaceous matters bear as chemical 

 characteristic the inclusion of hydrogen and oxygen in such 

 proportions that the oxygen could suffice exactly to saturate the 

 hydrogen and to transform it into water. The general formula 

 of these groups would therefore be C"'(H°0)''.i 

 ■■ Wurtz, Chimie Novmelle. 



