CHAPTER XXIV. 



FUNGI. INTRODUCTORY. 



The character which all Fungi have in common is a negative one : 

 the absence of chlorophyll, or of any kindred colouring matter by means 

 of which they can carry on photosynthesis. They are therefore 

 sometimes called colourless ; but many of them, and especially the 

 large Toadstools, are brightly coloured, though with pigments quite 

 distinct from chlorophyll. The absence of chlorophyll is associated 

 with the fact that they are able to acquire their supplies indirectly : 

 that is, either by a parasitic or a saprophytic habit. These methods 

 of nutrition have already been discussed in Chapter XII., as they 

 are seen in Seed-bearing Plants. A mere negative character, such 

 as the absence of chlorophyll, is not in itself a sound basis for classifica- 

 tion. At once the doubt is aroused whether all the Fungi are really 

 " blood-relations." Such Phanerogamic parasites and saprophytes 

 as were described in Chapter *XII. are without chlorophyll. But 

 they are for the most part referable to well-known Natural Families, 

 a fact which signifies that their ancestors were green, and that the 

 parasitic or saprophytic habit was adopted relatively late in the 

 Evolutionary History, after the seed-habit was already established. 

 No one would suggest that these plants should be ranked as Fungi, 

 nor assume that they are all " blood-relations." 



It is probable that a like story accounts for the origin of the Fungi, 

 and that they also sprang from self-supporting ancestors. But there 

 is reason to believe that at least the majority of them adopted irregular 

 nutrition early. The opportunity for parasitism and saprophytism 

 was open from the earliest times, wherever organisms grew closely 

 crowded, or their decaying bodies were massed together. The study 

 of fossil plants has shown that organisms characteristically fungal 

 existed from the earliest geological horizons from which there is any 



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