IRREGULAR NUTRITION 



10 = 



11 these respects Fungi are better cqiiii)})c.l iIkiii (.r<linary ^rvcn 

 :*lants, and it is this which makes a coaHtion with tlicni d i)Iiysiological 

 idvantage. ]\Iycorhiza may 

 ;ven lead indirectly to a state 

 )f saprophytic nutrition. 



Two different types of this 

 :oalition are recognised. In 

 ;he first the fungus lives out- 

 side the tissues of the plant 

 \^ith which it is related ; this is 

 Jescribed as ectotrophic, and it 

 occurs in the Beech, Horn- 

 Deam, Oak, and Scots Pine ; 

 ilso in Monotropa, and Sarcodes 

 Tig. 147). In the second the 

 iungus penetrates the tissues, 

 ind it is accordingly styled 

 3)idotrophic ; it occurs in thc\ 

 Heaths and Orchids, and in 

 the Club-Mosses and Adder's- 

 toneues. 



{a) EcTOTROPHic Mycoriiiza. 



Externally roots showing 



eclotrophic 7nycorhiza appear 



wrapped round by a covering 



of fungal origin, and are short 



and thick, and repeatedly 



branched. The branching is 



sometimes endogenous as in 



ordinary roots ; but in oth.cr 



:ases it is of external origin, 



^vith transition to forking in 



he Scots Pine. Sections show 



hat the roots are covered by 



I thick felt of matted fungal 



breads, which sometimes stop 



hort of the tip [Monotropa), 



)ut usually cover it com- 



ilctely (Pifius, Fagiis, Carpimis, 





luv. \\7- 

 Wholi- |>l.int of Sara^les, shrmini: 

 ro(U-syst<-iii, from which ariMs .1 t.utkx 

 sluxit. with liroad shcalhiiij; - 

 niinaliii'lon^srciVT wilh pr.Miu 

 (Aft.T nlivir.) 



