CHAP. II.] CHEMISTRY, ETC., OF PLANT LIFE. 87 



in this connection being the close morphological or struc- 

 tural agreement with species that yet produce chlorophyll. 

 As examples of saprophytes may be mentioned the 

 numerous species of fungi popularly known as " toad- 

 stools" that grow on rotten wood, manure, etc., also 

 other species of fungi, as the common mushroom (Agaricua 

 ca/mjpestris) , that grow on the ground, and which might 

 be supposed to feed on inorganic food like green plants; 

 but this is not the case, the mycelium of the fungus 

 absorbs organic food supplied by decaying vegetable 

 matter present in the soil. Amongst saprophytic flower- 

 ing plants found in Britain may be mentioned the bird's- 

 nest orchis {Neottia nidus-avis) , and the coral-root orchis 

 .{Gorallorhiza innata). 



Typical parasites and saprophytes, having no chloro- 

 phyll, never remove carbonic dioxide from the atmosphere, 

 neither do they give out oxygen, but act like animals in 

 removing oxygen and giving off carbonic dioxide in the 

 act of respiration. Such plants are not influenced by light 

 in connection with nutrition. 



Comparing saprophytes and parasites with plants pro- 

 ducing chlorophyll, it will be observed that the former 

 class save a considerable amount of labour by obtaining 

 their food more or leas ready made, but this gain is more 

 than neutralized by a loss of individuality and freedom, 

 and are necessarily more limited in their distribution. 

 A green plant can establish itself wherever there is a 

 supply of moisture, proper soil, and a suitable tempera- 

 ture ; the atmosphere being everywhere is not a deter- 

 mining factor. The parasite requires all the above 

 conditions to enable its host to be present, plus the host; 

 and as many parasites have become so specialized as to be 



