OCCURRENCE OF ECTOTROPHIC AND ENDOTROPHIC MYCORRHIZAS IN FOREST TREES

A short paper noting on the uncertainty of the relationship between taxonomic position and the form of mycorrhiza and recording a recent case of double infection in Lawson cypress (Cbamaecyparis lawsoniana PaiL) in the south of England. FRANK'S (i) classification of mycorrhizas into ectotrophic and endotrophicforms is still accepted in botanical textbooks, and although the separation of these two types may sometimes appear rigid and inadequate (Rayner, 2; Harley 3), it is nevertheless generally convenient and informative. There are a number of lists available supplying the names of plants regularly affected by one or other of these two forms of mycorrhizal infection, but this classification into ectotrophic and endotrophic plants is useful only so long as comparison is made with typical examples of these types. It has long been recognized (1) that while the endotrophic form is widely distri-buted among numerous plant species, the ectotrophic form seems to be re-stricted to certain forest trees and shrubs: the Pinaceae, Fagus, Betula, Corylus, Quercus, and many other members of the Fagales [presence of ectotrophic mycorrhizas in wild fruit-trees has been reported by Stahl (4) and described b