THE ROOT 183 
MycorRHIZA 
The roots of many plants, especially those growing in humus, 
are associated with fungal hyphz which form a weft over their 
surface, as in the case of the beech, etc., when this weft is called 
an ectotrophic mycorrhiza, or the surrounding hyphz may penetrate 
into the cells of the roots, as in many plants of the Heath and 
Orchid families, when the association is termed an endotrophic 
mycorrhiza. 
There are a number of plants, particularly non-green seed 
plants, which cannot thrive without the mycorrhiza with which 
their roots are normally associated and die when transplanted to 
soil not containing them. Mycorrhizz assist the roots to absorb 
nutrient materials from the soil. 
A number of mushrooms form ectotrophic mycorrhizas on 
the roots of trees. 
