IRREGULAR NUTRITION 



195 



In these respects Fungi are better equipped than ordinary green 

 Plants, and it is this which makes a coalition with them a physiological 

 advantage. Mycorhiza may 

 even lead indirectly to a state 

 of saprophytic nutrition. 



Two different types of this 

 coalition are recognised. In 

 the first the fungus lives out- 

 side the tissues of the plant 

 with which it is related ; this is 

 described as ectotrophic, and it 

 occurs in the Beech, Horn- 

 beam, Oak, and Scots Pine ; 

 also in Monotropa, and Sarcodes 

 (Fig. 147). In the second the 

 fungus penetrates the tissues, 

 and it is accordingly styled 

 endotrophic ; it occurs in the 

 Heaths and Orchids, and in 

 the Club-Mosses and Adder's- 



ngues. 





;) ECTOTROPHIC MYCORHIZA. 



xternally roots showing 

 ectotrophic mycorhiza appear 

 wrapped round by a covering 

 of fungal origin, and are short 

 and thick, and repeatedly 

 ranched. The branching is 

 etimes endogenous as in 

 inary roots ; but in other 

 es it is of external origin, 

 th transition to forking in 

 e Scots Pine. Sections show 

 t the roots are covered by 

 thick felt of matted fungal 

 ireads, which sometimes stop 

 short of the tip (Monotropa), 

 )ut usually cover it 



FIG. 147- 



Whole plant of Sarcodes, showing the mycorhizic 

 root-system, from which arises a bulky flesh-coloured 

 shoot, with broad sheathing scales below, and a ter- 

 lir^7>/.,, - E 1 ,. - /- j.V minal inflorescence with prominent bracts. Reduced. 



pletely (Pmus,Fagus t Carpmus, (After ou^,.., 



com- 



