THE 
HEW PHYTOIiOGIST. 
Vol. XV, No. 8 . October, 1916 . 
[Published November 30th, 1916], 
RECENT DEVELOPMENTS IN THE STUDY OF 
ENDOTROPHIC MYCORHIZA. 
By M. Chevely Rayner. D.Sc. 
S INCE the middle of the 19th century it has been recognized 
by botanists that invasion of the roots of a vascular plant by 
fungal hyphse may take place regularly without implying parasitism 
of the kind which is ordinarily responsible for the symptoms of 
disease. During the latter part of the century many cases of regular 
association between the roots of one of the higher plants and the 
vegetative stage of a fungus were described, and the view was 
clearly formulated by Pfeffer and others that such a condition 
involved a ‘ community of interest ’ on the part of the two organisms. 
The existence of such mutual relations had already been 
recognized in the lichens. In this group de Bary had described 
lichen species which show intimate relations between the algal and 
fungal constituents as regards nutrition, indicated by the formation 
of fungal haustoria which penetrate the algal cells. Such species 
are connected by transition forms with the commoner types in 
which the ‘ balance of power ’ is more evenly maintained either by 
increased resistance on the part of the algal cell or decreased 
demands on the part of the fungus. De Bary described the state 
of affairs among the lichens as a condition of symbiosis and the use 
of the term was soon extended to other cases of more or less evident 
mutualism in both plant and animal kingdoms. 
The regular association of mycelium with the roots of vascular 
plants noted by Kamienski (1881) and others was recognized as a 
case of this kind and the name mycorhiza used to describe it by 
Frank in 1887 has since passed into common botanical usage. 
The researches of Frank, his recognition of two types of 
mycorhiza which he named ectotrophic mycorhiza and emiotrophic 
mycorhiza respectively and the conception of symbiosis which he 
founded have become an integral part of the literature dealing with 
