SAPROPHYTES 241 



humus soils. Between these and typical saprophytes inter- 

 grades exist, so that it is likely that there are many cases of 

 partial saprophytism which have not been recognised. Or 

 we may look at the relation in another way. It is not certain 

 that any saprophytes really draw organic food directly from 

 the soil. The fungus may in all cases act as an inter- 

 mediary. The word " saprophyte " would thus be a 

 misnomer, and these plants would properly be regarded as 

 the end of a series, exhibiting the extreme results of the 

 mycorhizal habit, having become parasitic on their fungi. 

 It is, however, convenient at present to distinguish some 

 humus plants which have reduced leaves and chlorophyll 

 as a separate class. 



Systematic. — While there are no parasitic monocotyledons 

 the majority of saprophytes belong to that group. They 

 occur in the families Orchidaceae, Burmanniaceae, and 

 Triuridaceas. Among the dicotyledons the families Piro- 

 laceas (sometimes included in the Ericaceae), Gentianaceae, 

 and Polygalaceae, include saprophytic species. Among the 

 gymnosperms neither parasites nor saproph5^es are known. 



(a) Polygalaceae : the 2 species of Epirrhizanthes of the 

 Indo-Malayan region are saprophytes. 



(b) Gentianaceae : of the 60 genera of the family six, 

 which occur in four different tribes, with in all about 

 30 species, are saprophytes. The North American Bartonia 

 and Obolaria have sufficient chlorophyll to give them a 

 distinct green tinge, and may be regarded as partial sapro- 

 phytes. The rest, with a distribution that includes tropical 

 America and Africa, the West Indies, Ceylon, and the 

 Himalayas, are devoid of chlorophyll. In all cases the leaves 

 are represented only by scales, often of minute size. 



(c) Pirolaceae : 8 of the 10 genera, with 10 species, 

 are saprophytes, without chlorophyll and with only scale 

 leaves. Typically they inhabit the leaf mould of woods. 

 Thus, MonotropaHypopithys, the bird's-nest, occurs in beech 

 and fir woods in Britain ; Monotropa uniflora is the Indian 

 pipe of North American woods. The flowering shoots arise 

 from buds produced by the roots. Parasitic connections 



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