322 OF BROWN PARASITES. [BOOK ir. 



Teucrium, did not afford a trace of carbonic acid, whilst that 

 breathed by the Orobanche was found to consist of 



Nitrogen .... 100 



Oxygen .... 9'35 



Carbonic acid . . 37 '75 



whence it is evident that the proportion of carbonic acid 

 increased considerably, in the same quantity by which the 

 oxygen diminished. 



Plants then without green organs, are only incessantly 

 yielding to the atmosphere a part of their carbon, with a 

 small proportion of nitrogen and hydrogen. Far from ex- 

 tracting from them the elements of their nutrition, as green 

 plants do, they obtain all their substance from the soil. 

 Hence, doubtless, arises the necessity of their being parasites, 

 as the greater part of them certainly are. As to the doubtful 

 parasites, the Neottia nidus-avis and the Monotropa hypopitys, 

 can we not suppose that they have the power of reorganising 

 for their own use the immediate products of the decomposi- 

 tion of the vegetable matters, so abundant in the fresh woody 

 places in which they grow ? Would it not be partly the same 

 with true parasites, often developed to so great a degree 

 relatively to the extent of their points of contact with the 

 mother plant, with the Lathrsea squamaria for example? 

 For these sort of plants, as well as for Cryptogams alike with- 

 out green parts, complete parasitism, or this sort of indirect 

 parasitism, is the only method of nutrition." 



