194 BOTANY OF THE LIVING PLANT 



live system is reduced to the level seen in parasitic Fungi. But when 

 flowering follows, large buds are formed deep down in the tissue of 

 the host. These burst through, and develop as flowers (Fig. 145). 

 In Rafflesia Arnoldi each flower is thirty inches across when full blown, 

 and has a very peculiar and complex structure (Fig. 146). It thus 



FIG. 146. 

 Flower of Rafflesia Arnoldi. Much reduced. (After Robert Brown.) 



appears that while in parasites the vegetative system shows reduction, 

 which may at times reach an extreme, as in Rafflesia, the flower may 

 nevertheless be disproportionately large and elaborate, and produce very 

 numerous seeds. Biologically their number may be held as an offset to the 

 risk of not finding the proper host on germination. 



MYCORHIZA. 



Many Plants which look like normal autophytes prove on examina- 

 tion to have irregular nutrition, following on a state which is called 

 mycorhiza. But this, as it more particularly affects the roots, may not 

 be visible above ground. Trees such as the Beech, Hornbeam, Oak, 

 and Scots Pine are examples. In certain families it is prevalent, as 

 in the Heaths and Orchids. A similar mode of nutrition is often 

 present in the Club-Mosses and the Adder's-tongue Ferns, and it 

 occurs also in some Liverworts. Thus it is not restricted to any 

 single family, or even group of Plants. 



It consists in a coalition between fungal filaments and the living 

 tissues of another plant. Fungi have special powers of absorption 

 of certain substances from the medium in which they grow. They 

 extract soluble salts readily from the soil. They are also able, in 

 accordance with their usually saprophytic life, to acquire organic 

 material in the combined form from a substratum which contains it. 



