IRREGULAR NUTRITION 227 



level seen in filamentous 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. 154). In Rafflesia Arnoldi each flower is thirty inches across 

 when full blown, and has a very peculiar and complex structure (Fig. 155). 



Fig. 155. 

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



It thus appears that while in parasites the vegetative system shows reduction, 

 which may at times reach an extreme as in Rafflesia, the flower may never- 

 theless 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. 



Mycorrhiza. 



The roots or other underground organs of many flowering plants 

 regularly grow in close association with the filaments (or hyphae) of 

 a fungus : the term Mycorrhiza is applied to this association. There 

 is evidence that at least in some cases of mycorrhiza the higher 

 plant gains organic food and so displays an irregular nutrition. The 

 mycorrhizal association has usually been regarded as an example of 

 Symbiosis (or " living together ") from which both higher plant and 

 fungus derive benefit, but at present we are not in a position to assess 

 with any certainty the extent of such benefit. Probably any advan- 

 tage accruing to the higher plant is connected with the special sapro- 

 phytic faculty which the fungal partner has of absorbing organic 

 materials from the decaying vegetable matter of the soil. Some of 

 these materials, or derivatives of them, may become transferred from 

 the fungus to the higher plant with which it is associated in the 

 mycorrhiza. Indeed in those higher plants described as Complete 



